6570 



Crustacea. 



Fig. 3, — Zoe free from embryonic tunic. 



to be adults, the seas 

 would be swarming 

 and running over 

 with crabs, so great 

 are the number born. 

 Attached to a com- 

 mon edible crab, and 

 that of very moderate 

 dimensions, we cal- 

 culated two millions 

 of ova, and when we 

 consider that they 

 are capable and pro- 

 bably do have two or 

 more broods in a 

 year, we cannot but 

 consider that the 



enormous creation of young animal life is designed as food to older 

 and stronger creatures. 



The egg is wrapped within a strong circular case, and this is attached 

 to the parent, and carried by her beneath her tail, or curtain, or flap 

 (the pleon). There is a mystery in the attachment of the ova to the 

 parent : how they get there, and how they are attached we know not ; 

 they are suspended every one by a thread, and that thread to another, 

 and so on, each thread suspending an ovum ; thus, like a bunch of 

 grapes, thousands hang in a mass, and each mass 

 is suspended from the hairs which are attached 

 to the swimming feet {pleopoda). 



These organs (the pleopoda) vary, in the 

 female, from those of the male ; in fact, they are 

 mostly absent in the male crab (Brachyura), and 

 are short, broad, double plates in the lobster 

 (Macroura). In the female they consist each of 

 two long appendages, the inner one straight, the 

 outer slightly curved, and both fringed with hairs : 

 it is the inner one to which the ova are suspended. 

 When the egg is first deposited it probably is 

 covered by gelatiuous secretion, which forms the 

 protection over each, and hardens into the 

 Fto.4.— one of the pleopoda, thread by which it is suspended; but why they 



or false feet, with a few , • , . T 



ova attached. are suspended to the hairs upon the one branch 



