Mr. C. Spence Bate on the Development ofPagurus. 115 



antenna is developed upon the brachyurous type; but the 

 inferior has the squamiform appendage of the macrurous 

 Crustacea. So have all the other appendages that pertain to 

 the cephalon and pereion, except the last pair of pereiopoda ; 

 and these are not developed, at least they were not percep- 

 tible to our examination — a circumstance that would accord 

 with the animal being an undeveloped anomurous crusta- 

 cean. The pleon and its appendages bear a very close resem- 

 blance to those of the larva of a prawn, since it is equi- 

 laterally developed and furnished with a pair of appendages, 

 posteriorly and ventrally, attached to each somite, the last of 

 which is much larger than the others, and is evidently a pro- 

 gressive stage in the development of the great caudal plates of 

 the macrurous Crustacea. 



We attribute it to the genus Pagurus rather than to any of 

 our other anomurous Crustacea, because it differs from the 

 known zoea of Porcellanaj and of that of Galathea we have no 

 knowledge ; but from the nearer approach of these last genera 

 to each other in their adult stage than to Pagurus ^ we are in- 

 clined to believe in a nearer resemblance of their larvae. Hence 

 our assumption that this present immature species is a young 

 Paguriis. 



The next stage to which we allude (PI. IX. fig. 3) is one 

 which we noticed in our preliminary Report to the British 

 Association. 



The animal is a small creature that was taken floating near 

 the surface of the sea, in a warm day in June. Its general 

 appearance is that of a young macrurous crustacean, and as 

 such it has been classified near to GalUanassa and Calliadina. 

 It is symmetrical, except in the larger development of the 

 great chela of the right side. The two succeeding pereiopoda 

 are very long, but simple in their formation ; the last two are 

 considerably reduced in size, and the anterior terminates in a 

 small imperfectly didactyle forceps,while the posterior has a 

 copious terminal brush, consisting of cilia and short and broad 

 spines, amongst which the short, obtuse, and spinous dactylos is 

 discernible. The pleon is well developed, having each somite 

 clearly defined, and all, except the first, carrying an equally 

 developed pair of appendages, each of which consists of a 

 peduncle and two unequal rami. The posterior pair, or uro- 

 poda, differ from the others in having the peduncle shorter 

 and the outer ramus longer and more robust; it is likewise 

 slightly curved, in the older specimens, more on the left side 

 than on the right. 



In this condition they probably continue until they find a 

 suitable molluscous shell in which to reside. I imagine that 



8* 



