114 Mr. C. Spence Bate on the Development o/Pagurus. 



observing that of P. platycheles (PL IX. fig. 4) , I have taken 

 advantage of the circumstance. It differs from the recognized 

 typical zoea of the common shore-crab ( Carcinus mcenas) in the 

 monstrous development of an anterior and two posterior cor- 

 nuous processes to the carapace, and in the formation of the 

 telson ; but in its complete character it offers an intermediate 

 condition between the brachyurous and macrurous Crustacea. 

 It has the appendages of the cephalon and pereion developed to 

 a similar extent with those of the Brachyura, whereas the telson 

 and carapace bear a nearer resemblance to the same parts 

 in the Macrura, from which they differ in degree only. In the 

 carapace, instead of the rostrum and the posterior angles of the 

 carapace being only just pronounced as in the macrurous zoea, 

 they are developed to a larger extent in the anomurous larvae, 

 and in the young of the Porcellance to nearly twice or three 

 times the length of the animal ; while the telson, instead of 

 being shaped like the caudal fin of a fish, has in the Anomura 

 the central portion sometimes produced to an angle posteriorly. 



Beyond this stage of the development of this species, or, I 

 believe, any species of the Anomura, we have no sure know- 

 ledge, except that which I stated relative to the genus Glauco- 

 thoe being a stage in the development of the genus Pagurus. 



The zoea of Pagurus (PI. IX. fig. 1) is probably tolerably well 

 known to carcinologists, but I am not aware of its having been 

 figured* or described. It has the anomurous character of a 

 pointed rostrum and a projecting point at each of the posterior 

 angles of the carapace, and the telson terminating in a gradu- 

 ally widening fishtail-like appendage, fringed with a few ter- 

 minal spines — the appendages being developed rather on the 

 type of those of the Brachyura thaii of the Macrura. During 

 our expeditions we have taken specimens that we believe to be 

 the zoea of the same genus still further developed ; we say be- 

 lieve to be, because it is only from analysis that we have come 

 to this conclusion, and have not the testimony of direct obser- 

 vation that the one is the older stage of the other. 



That which we take to be the second stage of the genus 

 Pagurus (PI. IX. fig. 2) was captured toward the end of 

 May, in a towing-net, in Plymouth Sound. From its general 

 appearance my first impression was that it was the young of 

 a PalcBmon ; but closer observation and a careful dissection 

 of its parts induced me strongly to believe that it is the 

 young of one of the anomurous group of Crustacea, — in the 

 first place, the form of the carapace ; in the next, the general 

 divergence of its appendages from and their resemblance to 

 those of the zoea of a macrurous Decapod. The superior 

 * [Likewise figured by Fritz Miiller, op. n't. p. 36, fig. 26.— Ed.] 



