The works of Francis Maitland Balfour, Volume 2 (of 4)

[185] The following is the classification of the Crustacea employed in the present chapter: I. Branchiopoda. { Phyllopoda. { Cladocera. II. Malacostraca. { Nebaliadæ. { Schizopo...

The remarkable researches of Moseley (No. 396) on Peripatus capensis have brought clearly to light the affinities of this form with the tracheate Arthropoda; and its numerous pr...

Although the majority of important developmental features are common to the whole of the Mollusca, yet at the same time many of the subdivisions have well-marked larval types of...

The complete developmental history of any being constitutes a cycle. It is therefore permissible in treating of this history to begin at any point. As a matter of convenience th...

Hydroidea. The most typical mode of development of the Hydroidea is that in which the segmentation leads directly to the formation of a free ciliated two-layered larva, known si...

The larva of Balanoglossus is known as Tornaria. The præ-larval development is not known, and the youngest stage (fig. 272) so far described (Götte, No. 569) has many remarkable...

The immediate result of the fusion of the male and female pronucleus is the segmentation or division of the ovum usually into two, four, eight, etc. successive parts. The segmen...

Although there is perhaps no group in the animal kingdom the ontogeny of which would better repay a thorough investigation than the Turbellarians, yet the difficulties to be ove...

At the close of segmentation (fig. 247 A) the egg has a nearly spherical form, and is constituted of a single layer of columnar cells enclosing a small segmentation cavity. The...

Most Chætopoda deposit their eggs before development. The Oligochæta lay them in peculiar cocoons or sacks formed by a secretion of the integument. Some marine Polychæta carry t...

In the preceding chapter the changes in the ovum were described nearly up to the period when it became ripe, and ready to be impregnated. Preparatory to the act of impregnation...

The development of the larvæ of Pedicellina is known from the researches of Hatschek (No. 299) far more completely than that of Loxosoma, though it does not apparently differ fr...

Embryology forms a large and important department of Biology. Strictly interpreted according to the meaning of the word, it ought to deal with the growth and structure of organi...

Although within the last few years greater advances have probably been made in our knowledge of the development of the Porifera than of any other group, yet there is much that i...

Nematoidea. Although the ova of various Nematodes have formed some of the earliest, as well as the most frequent objects of embryological observation, their development is still...

The groups dealt with in the present Chapter undoubtedly belong to the Arthropoda. They are not closely related, and in the case of each group it is still uncertain with which o...

The eggs of the Discophora, each enclosed in a delicate membrane, are enveloped in a kind of mucous case formed by a secretion of the integument, which hardens into a capsule or...

It is convenient for the purposes of embryology to divide the Gephyrea into two groups, viz. (1) Gephyrea nuda or true Gephyrea; and (2) Gephyrea tubicola formed by the genus Ph...

For our knowledge of the early stages in the development of the Brachiopoda we are almost entirely indebted to Kowalevsky[129] (No. 326). His researches extend to four forms, Ar...

The structure and development of these remarkable parasites in the renal organs of the Cephalopoda have recently been greatly elucidated by the researches of E. van Beneden; and...

In all the Metazoa the segmentation is followed by a series of changes which result in the grouping of the embryonic cells into definite layers, or membranes, known as the germi...

The discoveries of Kowalevsky (No. 378) confirmed by Bütschli (No. 376) with reference to the development of Sagitta, though they have not brought us nearer to a knowledge of th...

For many reasons a complete knowledge of the ontogeny of the Rotifera is desirable. They constitute a group which retain in the trochal disc an organ common to the embryos of ma...

Prototracheata, pp. 382-387. Myriapoda, pp. 387-395. Insecta, pp. 395-429. _Embryonic membranes and the formation of the layers_, pp. 400-406. _Formation of the organs_, pp. 406...

History of larval forms, pp. 459-511. _Branchiopoda_, pp. 459-465. _Malacostraca_, pp. 465-487. _Copepoda_, pp. 487-492. _Cirripedia_, pp. 492-500. _Ostracoda_, pp. 500-502. _Ph...

Formation of the layers and larval characters, pp. 225-273. _Gasteropoda and Pteropoda_, pp. 225-242. _Cephalopoda_, pp. 242-254. _Polyplacophora_, pp. 254-257. _Scaphopoda_, pp...