CRANGON VULGARIS. 143 



before any other appendages are outlined. Connected with 

 this area hy a slender peduncle is a circular area interpreted 

 as the "carapace." Unless this be what I have termed the 

 dorsal organ which will be described later, I have seen 

 nothing to compare with it in Crangon. The optic lobes 

 in Atyephyra are at about the same distance from the tho- 

 racico-abdominal area as in Crangon, but Ishikawa does 

 not represent the cords of small cells connecting them. 



Between the stage just described and the next, which I 

 designate as B (fig. 11) there occurs a gap in my material 

 but the changes which have occurred in the interval can 

 easily be understood. The embryonic area is now consid- 

 erably smaller than before (a subject to be mentioned 

 later), while its form has undergone considerable altera- 

 tion. The optic lobes are now larger than before and 

 more closely approximate, the broad area of undifferen- 

 tiated blastoderm which formerly existed between them, 

 (reaching back to the thoracico-abdominal area) having 

 disappeared except for a V-shaped Prolongation which ex- 

 tends between the optic lobes. These lobes are also much 

 nearer the rest of the embryo ; and the thoracico-abdominal 

 area shows the beginning of the differentiation which justi- 

 iies the name applied to it. The cords of cells uniting the 

 optic lobe with the restcf the embryo in fig. 10 have now 

 united in the median line to form part of the ventral surface 

 of the shrimp. The optic lobes at this stage are elsewhere 

 described, but the rest of the embryo needs further men- 

 tion. 



From the lateral cords a broad plate formed by their 

 Union has developed, with the mouth, a shallow pit (^mo) 

 near its anterior margin, while on either side is seen the 

 first rudiment of an appendage (/) which the subsequent 

 history shows to be the first antenna or antennula. It is to 

 be noticed that this appendage at this time is distinctly 



