160 BULLETIN OF THE 



in obtaining it by extracting the embryo prematurely from the egg. In 

 this case escape from the egg and the first moult appear to take place 

 simultaneously. 



The bursting of the egg-membranes is effected by the convulsive at- 

 tempts of the imprisoned embryo to extend its abdomen, which is closely 

 applied to the sternum within the egg. The forked tail first extricates 

 itself (PI. I. Fig. 1), the antennae then protrude through the breach thus 

 made (PL I. Fig. 2), and in a very short time the contortions of the ani- 

 mal have completely torn away the egg envelope. The embryo, swathed 

 in a delicate, perfectly transparent cuticle, now lies on the bottom of 

 the aquarium supinely awaiting its first moult. It is as yet incapable of 

 swimming about and taking food,' its only movements consisting of ex- 

 tension and flexion of the abdomen. It is not until the veil is cast off 

 that the animal loses its embryonic character, and assumes the part of an 

 active, free-swimming larva, with mouth parts adapted for seizing prey. 



On issuing from the egg, the young measures J mm. in length (PL I. 

 Fig. 3). Within the transparent cuticle the zoea may be distinctly seen 

 as it will emerge on the first moult. The cuticle is not conformable to 

 the underlying larval integument, as it has neither dorsal nor frontal 

 horns, and the antennae and tail are very different. The carapace does 

 not at first extend far enough back to cover the base of the swimming- 

 feet, so that the abdomen appears much longer relatively than it does a 

 short time after hatching. 



At the joints between the segments of the abdomen of the zoea the 

 cuticle does not follow the indentations, but otherwise rests conformably 

 upon it. The two prongs of the forked tail of the zoea are compressed 

 into a very small space by means of a complex folding produced by an 

 invagination of the middle third of the prongs, which does not involve 



J. V. Thompson, Phil. Trans., 1835, p. 359, PL V. 



Heinrich Rathke, Zur Morphologie, p. 97. 1837. 



C. Du Cane, Ann. Nat. Hist., VoL IIL p. 438, PL XL 1839. 



H. D. S. GooDSiR, Edinburgh New Phil. Jour., Vol. XXXIII. p. 181, PL III. 

 1842. 



M. P. Erdl, Entwicklung des Hummereies, p. 27, PL II. 1843. 



R. Q. Couch, "Ann. Rep. and Trans. Roy. Cornwall Polytechnic Soc. for 1843." 

 (I have not seen this memoir. Some account of it is given in Bell's History of the 

 British Stalk-eyed Crustacea, Introduction, pp. xlix. -liv., Figs, c, d, e, and pp. 

 79-81. 1853.) 



C. Spence Bate, Phil. Trans., VoL CXLVIII. p. 589, PL XL.-XLVI. 1859. 



V. Hensen, Zeitschr. Wiss. ZooL, VoL XIII. pp. 340, 362, PL XX. Fig. 25. 

 1863. (Auditory organ of the young.) 



Anton Stuxberg, Ofvers. Kongl. Vetensk.-Akad. ForhandL, XXX. (1873), No. 

 9, p. 7. 1874. ' 



