90 * THE VOYAGE OF H.M.S. CHALLENGES. 



No doubt there are large numbers in the sea, and these are occasionally taken, but 

 though the adult is common * on our south western coast, yet the Phyllosoma form has 

 only been taken occasionally as solitary specimens. In the warmer latitudes they have 

 been more frequently captured, from the length of 1*5 mm. to that of 30 mm., but 

 these being from different as well as distant localities are undoubtedly the young of 

 different species or perhaps even genera. 



The smallest, and as we may suppose the youngest form (PI. XIIa. fig. 2), taken by 

 the Challenger off Samboangan, is about l - 5 mm. in length, corresponding to that of the 

 young when it quits the egg. It differs from the more immature form (fig. 1) that I have 

 taken from the ovum of the European species, in having the vitellus entirely absorbed) 

 and in having the various hairs that fringe the appendages liberated from the embryonic 

 case and freely extended. The central eye or ocellus is distinct ; close behind (fig. 4) 

 and connected with it, is a small circular transparent body that I take to be a lens, 

 posterior to this again and lying transversely is a narrow fine of rigid integument that 

 I take to be the ventral surface of the first or ophthalmic somite. It extends from the 

 base of one ophthalmopod to that of the other, where it probably blends with the 

 membranous articulation. The ophthalmopod is long and cylindrical, and suddenly 

 expands at the base of the ophthalmus. On each side of the median line, a little posterior 

 to the ventral ridge of the first somite, are two small bodies that appear to be the nuclei of 

 a mass of nerve matter that surrounds them. This neural substance passes back in two 

 gradually narrowing lines, one on each side of the oral apparatus, from whence I was not 

 able to trace it until it reaches the pereion, where it reappears in the form of three 

 double lobes corresponding with the three posteriorly developed pairs of pereiopoda. 

 The mandibles possess a rigid character and a long calcified tendon that extends nearly 

 to the base of the second pair of antennas. I have not been able to determine wdiether 

 the synaphipod be present, neither can I determine in this solitary specimen whether the 

 first pair of siagnopoda be developed. The first pair of pereiopoda consists of a small, 

 unbranched, well-formed appendage, it has only six joints, very short, and terminates 

 in a sharp pointed dactylos. 



The second pair is also six-jointed, it is very much longer than the first, is biramose, 

 and terminates in a long and slender dactylos. 



The third and fourth pairs of appendages are seven-jointed and resemble each other, 

 except that I could only determine the presence of a long spine-like tooth at the distal 

 extremity of the ischium in the third pair, whereas in the fourth there is a prominent 

 one present on the basis, ischium and meros also. There is, moreover, a small branch 

 attached to the coxa ; this is homologous with the mastigobranchia in the adult animal, 

 and exists on the third and fourth pairs of pereiopoda, but not, so far as I could deter- 



1 The late Mr. Laughrin of Polperro informed me that one man took, a short time since, as many as sixty-four 

 in one night off Kedgwith near the Lizard, and frequently as many as fifty. 



