8 Crust. 
CRUSTACEA. 
6 . Generation and Development. 
The literature on development of Crustacea is enumerated by W. 
Faxon, Bull. Mus. C. Z. ix. No. 6, pp. 197-250. 
The three different modes of segmentation known hitherto in the 
Crustacea and Decapoda are discussed, and a fourth, viz., division of the 
nucleus in 16 parts, and afterwards formation of 16 cells on the outside 
of the yelk, observed in Callianassa, described by C. V. Mereschkowski, 
Zool. Anz. 1882, pp. 21-23, woodcut ; abstract in Arch. Z. exper. x. p. xv. 
Popular description of the metamorphosis of several Crustacea , by 
0. Taschenberg, Yerwandlungen der Thiere, Leipzig : 1882, pp. 106- 
121, 11 woodcuts. 
Metamorphosis of Alpheus ; W. Brooks, in J. Hopkins Univ. Circul. 
No. 17, p. 247. 
T. Tullberg, Sv. Ak. Handl. xix. No. 3, pp. 5-12, pi. i., discusses the 
structure and development of the cephalothorax of Homarus vulgaris , 
coming to the following conclusions : — 
1. The greatest part of the chitinous integument is formed by successive 
transformation of the outer parts of the cells of the matrix, these cells 
splitting into fibres, and depositing at the same time a stratified inter- 
mediate substance between them. 
2. The outermost layer, which is not transversely striated, has its origin 
probably also in the transformation of the cells of the matrix, with or 
without previous formation of fibres. 
3. The intimate connection of the chitinous integument with its matrix 
is caused by the cells themselves growing into the shell. 
4. The so-called pore-channels are not situated within the fibres nor 
can they be seen beside them in a transverse section ; they have a very 
irregular aspect and originate probably during the drying of the shell. 
7 . Moulting . 
A. N. Vitzou has examined the minute structure and chemical com- 
position of the integuments of the Decapods before, during, and after 
the moult ; and comes to the conclusion that the chitinous shell is formed 
by the thickening of the [external walls of the cells, the epithelium of 
which becomes chitinogene, that glycogene is always present in the skin, 
but more copiously during the moult, and that it may serve as reserve 
material for the new formation of the organic parts of the skin, the in- 
organic materials being accumulated in the crayfish and lobster in what 
is called the lateral wall of the stomach, in other Decapoda in the lym- 
phatic fluid itself. Arch. Z. exper. x. pp. 431-577, pis. xxiii.-xxviii. 
F. Mocquard publishes some observations on the solution of continuity 
in the apodemes caused by the moult. C. R. xcvi. pp. 204 & 205. 
8 . Biology. 
L. Fredericq states that the loosening of the limbs in Carcinus mcenas 
is confined to distinct joints, where it occurs spontaneously, if any vio- 
