No. 2.] EMBRYOLOGY OF THE AMERICAN LOBSTER. 239 



Stage J. 



Changes from the preceding condition are striking, and take 

 place very rapidly. Indeed, I have found but few eggs that 

 show an intermediate stage of development. The appendages, 

 earlier seen as irregular clouds, are now more clearly outlined, 

 and the thoracico-abdominal fold is (PL XIV, Fig. /, TJi. Abd) 

 considerably elevated, the place of the future anus being indi- 

 cated at A. The stomodaeum has also appeared (St.), and 

 occupies a position midway between the first pair of antennae 

 (An. 1 ). Lying immediately posterior are the diverging second 

 antennas (An. 2 ). The mandibles, the origin of which was noted 

 in I, are seen to occupy a position between the second antennae 

 and the thoracico-abdominal plate. All the so-called "nauplius 

 appendages" are, then, present in outline. 



If alcoholic eggs are examined, the annoying condition of the 

 " Blastodermhaut" of the previous stage is found to exist no 

 longer, but the membrane lies entirely free from the enclosed 

 egg. The nuclei of the embryo are now free to select the 

 stain, and most beautiful preparations are easily made (PL 

 XVII, Fig. 1). 



Each procephaiic lobe is abruptly elevated above the surface 

 of the egg by the furrows (fur.) already noted for the previous 

 stage, and its anterior portion (Ce), more highly nucleated and 

 slightly concave, represents the rudimentary compound eye. 

 A slight diagonal- depression separates it from the more cen- 

 tral portion, the ganglionic elevations (C7. 1 , G. 2 ). At the poste- 

 rior outer corner of the eye triangle a small pit is to be noticed. 

 Its signification I cannot give. Within the ganglionic portion 

 just mentioned, and anterior to the stomodaeum, the slight ele- 

 vation of the upper lip can be seen. 



At the base of the antennae, and lying on either side of the 

 stomodaeum, are the ganglia of the first antennal segment 

 (G. s ). Immediately posterior to them are the connecting lines 

 of nuclei which unite them with the corresponding elevations of 

 the second antennae (6\ 4 ). The antennae are abruptly elevated 

 along their anterior border and exhibit a tendency to form 

 joints. The groove that separates the antennas from the pos- 

 terior and lateral edges of the procephaiic lobes, in favorable 

 specimens, shows the presence of an elongated crescentic eleva- 



