CBUSTACEA. 479 



Its peculiar form, and the failure up to the present time, of 

 tracing the animal through all its stages of development, makes 

 it an object of interest; and I think it worthy of consideration, 

 particularly by those who, as a crucial test in the theory of 

 evolution, demand the exposition of a series of successional 

 forms of life. They should remember that of this animal so com- 

 mon on our coast and in our markets, that there is no one yet who 

 has been able to determine the several forms through which this 

 animal passes in its growth from the zoea to the adult stage. 

 Its first form is that known as Phyllosoma, its next stage is, I 

 believe, that known as the genus AmpMon, but this is only con- 

 jecture, as it has not been traced or clearly determined beyond 

 the form the young quits the ovum. How, therefore, if a common 

 form like this Crawfish cannot be traced from one end of its life 

 to another, can we expect that the record of many forms of lost 

 animals can be made perfect ? 



The young quit the ovum mostly at the same time, and Mr. A. 

 Lloyd tells me that in the aquarium they suspend in the water 

 for a day or so like a monster cone-like cloud, after which they 

 disperse and die. 



IBALAMNIDM. 



Genus, Calliajstassa. — Leach. 



" The integuMents, except of the claw, less, soft ; caudal plates 

 large and foliaceous ; first pair of legs didactyle, unequal ; second 

 pair small, didactyle;" third pair not didactyle. Carapace with 

 rostrum. 



Callianassa sttbterranea. — Burrowing Shrimp. — Leach, Malae. 

 Brit. t. xxxii; Milne Edwards, Hist, des Crust., vol. ii, p. 3 and 9. 



Montague first took this species, probably, in Kingsbridge river; 

 I took it many years since in company with the late Professor 

 Kinahan, in Plymouth Sound. Mr. Couch makes no remark 

 about it, or says where it was taken, but most probably off 

 Polperro, but as it is a burrower it probably escapes observation. 



GrENTS, AxiTJS. — Leach. 



''Integuments moderately firm; caudal plates large and foli- 

 aceous. First pair of legs chelate, unequal ; second pair chelate, 

 subequal ; the following pairs not didactyle. Carapace with a 

 small triangular rostrum." 



