90 



becomes more and more obscure, and cannot certainly be recognised in the region of the 

 intestinal loop of the gut. I do not think that this forbids the assumption I have just indicated. 

 The thin-walled vessels of Cephalodiscus are very difficult to distinguish in their empty condition, 

 and the faikn-e to find a vessel in a particular case is no proof that it does not exist. It will 

 be remembered that, in the female Cephalodiscus, the posterior stalk-vessel ends in the wall of 

 the second stomach, and I have suggested above that its blood, after passing through the 

 sinuses of the alimentary canal, finally makes its way to the dorsal vessel. With the practical 

 disappearance, in the male, of the first and second stomachs, the posterior stalk-vessel might 

 still retain its function of supplying the dorsal vessel. On a priori grounds therefore it appears 

 to me probable that there is an indirect communication between these two vessels. 



(II) The function of the epidermic vesicles of the arms of the male. 



I think there can be little doubt that these .structures are homologous with the vesicles 

 which occur in the end-bulbs of the arms of the females of certain species, and especially of 

 C. dodecalophus. I have not found them in C. Icvinseni, but they are well developed in the 

 anterior pairs of arms in the buds of C. gracilis, and sometimes at least they persist in the 

 adults of that species. 



I have in one or two cases noticed appearances (PI. IX, fig. 98) for which I cannot 

 quite account, in C. sibogae. An ordinary tentacle-bearing arm has been found, in a partially 

 teased preparation, with its distal end prolonged into an elongated, vesicle-bearing portion without 

 tentacles, similar to the entire arm of a male. I think there is little doubt that this is a correct 

 observation, though in view of the tangled condition of the zooids the possibility is not quite 

 excluded that the arm of a male has adhered to that of a neuter by defective preservation. 

 There is, however, practically no doubt that the arm shewn in fig. 98 is in continuity with an 

 individual which bears tentaculiferous arms and has the general characters of a neuter. But it 

 also appears that the metasome of this individual contains, in the position occupied by the 

 ovaries of an ordinary Cephalodiscus, a pair of small testes, which seem to be functional organs. 

 I therefore regfard this case as one of correlated variation, in which a zooid has not onlv the 

 male character of possessing testes but also the associated character of developing numerous 

 vesicles on one of its arms. I cannot, unfortunately, decide whether the abnormal arm belongs 

 to the first pair, though this is by no means impossible. It must further be pointed out that 

 there is some difficulty in disentangling a complete zooid from the inass of somewhat badly 

 preserved individuals found in the basal encrustation of the coenoecium ; and it is thus not 

 impo.ssible that all the neuters may have one or more of their arms prolonged into vesicle- 

 bearing portions. The evidence is, however, distinctly opposed tu any such view; and fig. 98 

 thus appears to represent an abnormality. 



If the vesicles of the male arms represent those of the end-bulbs of the arms of C. 

 dodecalophtts, it is probable that their function cannot be one which is exclusively correlated 

 with the other peculiarities of the male. This makes it less probable that the vesicles have the 

 nature of reserve-supplies of nutritive material, developed precociously in the young bud tor the 

 nutrition of the future testes. Some support might be given to this view by the fact that some 



