COMMON PEA-CRAB. 



125 



" As the females are found with an amazing group of 

 ova under their abdominal plate," says this author, " in 

 spring, summer, and autumn, it is probable that they have 

 several successive broods. This circumstance renders it no 

 difficult matter to select a number of females with mature 

 ova at any convenient time, and to preserve them alive 

 in sea water for a few days, or until the ova should hatch. 



" From several females selected and kept alive after the 

 above manner, I had the satisfaction to see the ova hatch 

 in great numbers, under the form of a new kind of Zoe, 

 differing from all those previously discovered, with the 

 front and lateral spines deflected, so as to resemble a tripod. 

 In this stage the minute animals are all like the Zoea, 

 purely natatory, disperse themselves abroad, probably un- 

 dergo a further change, and may be supposed to gain an 

 easy access within the bivalve shells, before they lose their 

 power of swimming.'*'' 



I add a copy of Mr. Thompson's figures of this interest- 

 ing state of the animal, the accuracy of which I can attest 

 from my own observation. 



