164 BULLETIN OF THE 



a long joint with a long and a short hair on its extremity (PL I. Fig. 

 10, b; PL II. Fig. 3, b). This is the homologue of the "scale" of the 

 antenna in Macroura, and appears to represent the main, triple portion 

 of the embryonic antenna (PL I. Fig. 10, b). 



The tail (PL II. Fig. 2) has now the form so characteristic of the 

 zoea of Brachyura. It is a forked piece, each prong of the fork bearing 

 three setae on the inner side near the base, and three minute ones on the 

 outer side. The prongs of this forked tail themselves are homologous 

 with the fourth spine of the embryo tail, as before pointed out. The 

 outer three (5, 6, 7) diminish in size successively. 



Although I succeeded in keeping some of these zoeae alive for seven 

 days, none passed through another moult. 



In Spence Bate's classic memoir on the development of Carcinus mce- 

 nas, the embryonic membrane which covers the zoea when it first quits 

 the egg is described and figured as conformable to the whole animal, 

 the tail and antennae not excepted. Thus are ignored the most inter- 

 esting and suggestive structural features of the embryo. This error of 

 observation is the more remarkable, since the structures in question were 

 figured with approximate accuracy twenty years before by that close 

 observer, Captain Du Cane.* 



H. D. S. Goodsirf also seems to have seen the same structures, al- 

 though his description and figures are very incorrect. The " curious 

 brush-shaped appendages of the embryo," which " drop off when the 

 animal has escaped from the ovum, and are replaced by spines," \ are evi- 

 dently the invaginated caudal spines of the embryonic cuticle, such as 

 are represented in our Plate I. Fig. 6. Spence Bate's identification of 

 the two pairs of swimming-feet of the zoea with the second and third 

 pairs of maxillipeds of the adult, instead of with the first and second 

 pairs, was not so strange ; but why does he persist in the old error, 

 even in his latest papers,§ after it has been particularly pointed out by 

 Fritz Miiller,|[ Stuxberg,! Glaus,** and others'? 



* Op. cit., PI. XL Figs. 1, 5. 



t Edinburgh New Philosoph. Jour., Vol. XXXIII. p. 182, PL III. Figs. 16, 17. 

 1842. 



% Pp. 182, 191, PL III. Fig. 17. 



§ Keport on the Present State of our Knowledge of the Crustacea. Eep. Brit. 

 Assoc. Adv. Sci., 1875, p. 48 ; 1876, p. 89 ; 1877, p. 44 ; 1878, pp. 7, 8. 



|| Op. cit., Eng. Trans., p. 52. 



1[ Op. cit., p. 10. 



**"Wurzb. naturw. Zeitschr., 1861, p. 30. Untersuchungen zur Erforschung der 

 Genealogischen Grundlage des Crustaceen-Systems, p. 62. 1876. 



