228 EVENINGS AT THE MICROSCOPE 



which by its superior size seems to have made some prog- 

 ress toward maturity. 



Yes, here are more. These are evidently in their sec- 

 ond stage. There is an increase in length; for whereas 

 the former was only ifoyth of an inch in length, these have 

 attained to a length of irVth of an inch. Yet this increase 

 is observable in no other dimension than that of total 

 length, and this is due to the development of the terminal 

 spine of the shield, which is now much produced, and 



YOUNG OF BARK ACLB. 



cat into minute teeth. The anal fork is also attenuated, 

 lengthened, and bent abruptly downward at the base, 

 where it is very mobile ; another bend in the middle throw- 

 ing the extremity into the horizontal again. The deli- 

 cately membranous pouch-like proboscis is more clearly 

 seen beneath the breast, the extremity of which is directed 

 backward. In front of this organ there are two decurved 

 very mobile bristles, set on pedicles, the whole closely 

 resembling the internal antenna in the higher Crustacea. 

 The lateral horns or external antennas appear to terminate 



