The works of Francis Maitland Balfour, Volume 3 (of 4)

The alimentary canal in the Chordata is always formed of three sections, analogous to those so universally present in the Invertebrata. These sections are (1) the mesenteron lin...

One of the most important recent embryological discoveries is the fact that the central nervous system, in all the Metazoa in which it is fully established, is (with a few doubt...

Excretory organs consist of coiled or branched and often ciliated tubes, with an excretory pore opening on the outer surface of the body, and as a rule an internal ciliated orif...

The variations in the character of the embryonic development of the Amniota are far less important than in the case of the Ichthyopsida. There are, it is true, some very special...

The classical researches of Bischoff on the embryology of several mammalian types, as well as those of other observers, have made us acquainted with the general form of the embr...

It has already been shewn in the earlier chapters of the work that during the first phases of development the history of all the Metazoa is the same. They all originate from the...

In the lowest forms of animal life the whole surface is sensitive to light, and organs of vision have no doubt arisen in the first instance from limited areas becoming especiall...

In the Coelenterata no body cavity as distinct from the alimentary cavity is present; but in the remaining Invertebrata the body cavity may (1) take the form of a wide space sep...

In the Solitaria, except Cynthia, the eggs are generally laid, and impregnation is effected sometimes before and sometimes after the eggs have left the atrial cavity. In Cynthia...

Three distinct sets of elements may enter into the composition of the skull. These are (1) the cranium proper, composed of true endoskeletal elements originally formed in cartil...

Although the preceding chapters of this volume contain a fairly detailed account of the early developmental stages of different groups of the Chordata, it will nevertheless be a...

In the case of all aquatic forms, or of forms which have directly inherited their auditory organs from aquatic forms, these organs are built upon a common type; although in the...

Pisces. Amongst Fishes the pectoral girdle presents itself in its simplest form in Elasmobranchii, where it consists of a bent band of cartilage on each side of the body, of som...

The impregnation of the ovum is effected in the oviduct. In most forms the whole of the subsequent development, till the time when the embryo is capable of leading a free existe...

The eggs of most Amphibia[43] are laid in water. They are smallish nearly spherical bodies, and in the majority of known Anura (all the European species), and in many Urodela (A...

Amongst the products of that part of the mesoblast which constitutes the connective tissue of the body special prominence must be given to the skeleton of the Vertebrata, from i...

The present section of this work would not be complete without some attempt to reconstruct, from the materials recorded in the previous chapters, and from those supplied by comp...

[24] The present chapter is in the main founded upon observations which I was able to make in the spring of 1880 upon the development of Petromyzon Planeri. Mr Scott very kindly...

It is only within quite recent times that any investigations have been made on the embryology of this heterogeneous, but primitive group of fishes. Much still remains to be done...

The majority of the Teleostei deposit their eggs before impregnation, but some forms are viviparous, _e.g._ Blennius viviparus. Not a few carry their eggs about; but this operat...

In all the Coelenterata, except the Ctenophora, the contractile elements of the body wall consist of filiform processes of ectodermal or entodermal epithelial cells (figs. 375 a...

The structure and growth of the ovum and spermatozoon were given in the first chapter of this work, but their derivation from the germinal layers was not touched on, and it is t...

The formation of the germinal layers in the Reptilia is very imperfectly known. The Lizard has been studied in this respect more completely than other types, and there are a few...

each of the flattened surfaces there was a spot free from villi. On the surface adjoining the uterine wall was a darker area (_e_) formed of two layers of cells, which is interp...

The developmental history of the Chordata has been studied far more completely than that of any of the groups so far considered; and the results which have been arrived at are o...

Protective epidermal structures. These structures constitute a general cuticle or an exoskeleton of scales, hairs, feathers, nails, hoofs, &c. They may be entirely formed from t...

Our knowledge of the development of the organs in most of the Invertebrate groups is so meagre that it would not be profitable to attempt to treat systematically the organogeny...

... and pushed in in its middle ... Footnote 163 - added final 's' to 'Nervensystems' Fig. 100 - added 'yolk' as definition to abbreviation 'yk.' in caption Fig. 191 - 'Mc' to '...

In many of the Coelenterata the outermost layer of the blastoderm is converted as a whole into the skin or ectoderm. The cells composing it become no doubt in part differentiate...

Coelenterata, pp. 471, 472. Mollusca, pp. 472-479. Chætopoda, p. 479. Chætognatha, p. 479. Arthropoda, pp. 479-483. Vertebrata general, pp. 483-490. Retina, pp. 490-492. Optic n...

Auditory organs, pp. 512-531. General structure of auditory organs, pp. 512, 513. Auditory organs of the Coelenterata, pp. 513-515. Auditory organs of the Mollusca, pp. 515, 516...

Platyelminthes, pp. 680, 681. Mollusca, pp. 681, 682. Polyzoa, pp. 682, 683. Branchiopoda, p. 683. Chætopoda, pp. 683-686. Gephyrea, pp. 686, 687. Discophora, pp. 687, 688. Arth...

The body cavity, pp. 623-632. General, pp. 623, 624. _Chordata_, pp. 624-632. Abdominal pores, pp. 626, 627. Pericardial cavities, pleural cavities and diaphragm, pp. 627-632. B...

The origin of the nervous system, pp. 400-405. Nervous system of the Invertebrata, pp. 405-414. _Central nervous system of the Vertebrata_, pp. 415-447. Spinal chord, pp. 415-41...

The Pectoral girdle, pp. 599-606. Pisces, pp. 599-601. _Amphibia and Amniota_, pp. 601, 602. Lacertilia, p. 603. Chelonia, p. 603. Aves, pp. 603, 604. Mammalia, p. 604. Amphibia...

Introductory remarks on the origin of the skeleton, pp. 542-544. Bibliography of the origin of the skeleton, pp. 544, 545. The notochord and its cartilaginous sheath, pp. 545-54...

Preliminary remarks, pp. 564, 565. The cartilaginous cranium, pp. 565-571. The parachordals and notochord, pp. 566, 567. The trabeculæ, pp. 567-570. The sense capsules, pp. 570,...

Mesenteron, pp. 754-774. Subnotochordal rod, pp. 754-756. Splanchnic mesoblast and mesentery, pp. 756-758. _Respiratory division of the Mesenteron_, pp. 758-766. Thyroid body, p...

I. Mode of origin and homologies of the germinal layers, pp. 331-360. Formation of the primary germinal layers, pp. 332, 333. Invagination, pp. 333-335. Delamination, pp. 335-33...

Formation of the gastrula, pp. 275-292. The formation of the mesoblast and of the notochord, pp. 292-300. _The epiblast_, pp. 300-304. Formation of the central nervous system, p...

General considerations, pp. 311-316. The medullary canal, pp. 316, 317. The origin and nature of the mouth, pp. 317-321. The cranial flexure, pp. 321, 322. The postanal gut and...

Segmentation and formation of the layers, pp. 214-227. General growth of the embryo, pp. 227-232. Embryonic membranes and yolk-sack, pp. 232-239. Comparative history of the Mamm...

Generative organs, pp. 741-748. Porifera, p. 741. Coelenterata, pp. 741-743. Chætopoda and Gephyrea, p. 743. Chætognatha, pp. 743-745. Polyzoa, p. 745 Nematoda, p. 745. Insecta,...

_Acipenser_, pp. 102-110. Segmentation and formation of the layers, pp. 102-104. General development of the embryo and larva, pp. 104-110. _Lepidosteus_, pp. 111-119. Segmentati...

Evolution of muscle-cells, pp. 667, 668. _Voluntary muscular system of the Chordata_, pp. 668-679. Muscular fibres, pp. 668, 669. Muscular system of the trunk and limbs, pp. 673...

Oviposition and impregnation, pp. 120, 121. Formation of the layers, pp. 121-124. Epiblast, pp. 125-127. Mesoblast and notochord, pp. 128, 129. Hypoblast, pp. 129-131. _General...

_Solitaria_, pp. 9-23. Development of embryo, pp. 9-15. Growth and structure of free larva, pp. 15-19. Retrogressive metamorphosis, pp. 19-23. _Sedentaria_, p. 23. _Natantia_, p...

Segmentation and formation of the layers, pp. 145-166. General history of the germinal layers, pp. 166-169. General development of the embryo, pp. 169-180. _Foetal membranes_, p...

Segmentation and formation of the layers, pp. 40-47. Epiblast, p. 47. Mesoblast, pp. 47-51. Hypoblast and notochord, pp. 51-54. General features of the embryo at successive stag...