218 ETEXINGS AT THE MICEOSCOPE. 



domen is attaclied to it, as -is seen when the latter bends 

 down. Its extremity gradually tapers into two straight, 

 sub-parallel, stiff spines, about as long as the carapace 

 itself, each terminating in a hooked point. 



The abdomen ends in a spinous plate, which is very 

 elegantly lozenge-shaped, and beset with spines. Each 

 of the two latero-posterior edges of the lozenge is cut 

 into six rectangular teeth, and each tooth bears on its 

 hinder face a long spine articulated to it, and most del- 

 icately plumose all along its sides. The hindeiTaost 

 pau* of spines are short, and are set close together, side 

 by side. Besides these jointed spines, each lateral 

 angle of the caudal lozenge-shaped tail-plate projects 

 into a spine-like tooth. 



Thouo;h the individuals before us are all in the same 

 state as to the stage of their development, there is 

 some difference in size, indicating, doubtless, a corre- 

 sponding diversity in age. "We will isolate a few of the 

 largest, and put them into a glass trough for micro- 

 scopical examination. 



The largest, during the few minutes which I have 

 occupied in the process of dipping them out, has under- 

 gone a metamorphosis. You observed that, after skip- 

 ping about the trough for a few moments, it sank quietly 

 to the bottom, where it lay on its back ; the next thing 

 that you see is a much more crab-like animal, more 

 opaque, redder, much larger, but lying on its back in 

 the very spot where a moment before you had seen a 

 Zoea f while close by it lies the transparent filmy skin 

 which has been cast off. 



The new animal is evidently now in its final state, 

 needing only development of its parts, which it would 

 obtain, if in freedom, '^ly successive moults, to acquii-e 

 the adult form. 



