212 THE VOYAGE OF H.M.S. CHALLENGER. 



The podobranchial plume is absent from all the appendages except the first pair of 

 gnathopoda (h), where it is short but well formed, and attached to the base of a small but 

 efficient mastigobranchia that equals the podobranchial plume in length, and lies between 

 and separates the plumes of the first from those of the second pair of gnathopoda. 



Beneath the podobranchia lies one rather small and slender arthrobranchial plume, 

 which, from its position, I consider to be the posterior. But the examination of two 

 specimens, one from Bermuda, and the other from the Fiji Islands, has failed to show 

 the second or anterior arthrobranchia attached to this articulation, or a pleurobranchia 

 either. 



The second pair of gnathopoda (i) has a small mastigobranchia, no podobranchia, two 

 well-formed arthrobranchise, and a small pleurobranchia (omitted in the plate). 



The pereiopoda are similar in arrangement, but increase in strength and development 

 posteriorly, both as regards the mastigobranchial plates and the branchial plumes, until 

 the fifth or posterior pair of pereiopoda, where, as is common in the Macrura, the 

 pleurobranchia alone is present, and is more largely developed than any of the anterior 

 plumes. 



The branchial arangement may be thus tabulated — 



Pleurobranchias, 

 Artbrobranehiae, 

 Podobrancbiae, 

 Mastigobrancbiae, 



fa. i k 1 m n o 



Thus there are six pleurobranchiaa, eleven arthrobranchise (five anterior, six posterior), 

 one podobranchia, and six mastigobranchia, of which the first though small is the only 



efficient appendage, the others being more or less rudi- 

 mentary, but increasing in importance posterior to the first 

 pair of pereiopoda. 



Close observation of the specimens from the Eastern and 

 Western Hemispheres has failed to show the slightest varia- 

 tion, except in the curvature of the posterior pair of pereio- 

 poda, which, in the Bermudan specimen, from which our 

 figure is taken, has the meros bent and the carpos, so far 

 as preserved, not multiarticulate, features which I attribute 

 to some accident to the appendage during development. 



The ova are small in size, being only 0"5 mm. in diameter, 



Fig. 40.— Embryo of Stenopushis- 



pidus, as seen in the ovum. and enormous in number. An examination of the immature 



embryo shows there is reason to believe, from the advanced 

 stage in which it appears, that the brephalos may quit the ovum in the Megalopa 

 stage, which circumstance, although it does not coincide with the form of the brephalos 



