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



There were further no particulars, nor any features deviating from the general type 

 of Cerebratulus to be gathered from these fragments. 



Numerous other fragments, of which one was a head, were obtained at Kobe (Japan). 

 Three of these are figured on PI. XV. figs. 6, 7, and 8. Sections were duly made of these 

 fragments, but do not give much additional light beyond the general result that we have 

 a Cerebratulus before us, which cannot be definitely identified with any of the species 

 hitherto described. The vicinity of the Japanese waters to scientific centres from w r hich 

 accurate descriptions of the Japanese marine invertebrates may probably be expected 

 ere long, makes it all the more advisable to refrain for the present from creating or 

 identifying species from these regions of which sufficient data cannot yet be obtained from 

 the available fragments. Still the specimen figured on PI. XV. figs. 6 and 7 deserves some 

 attention. The fragment, on which longitudinal and transverse white stripes were 

 visible, as indicated in the figure, was also distinguished by a peculiar rigidity. Trans- 

 verse sections (PL XV. fig. 7) showed that this phenomenon was occasioned, or at all 

 events accompanied by, an extraordinary development of intermuscular gelatinous tissue. 

 The section figured, when compared with that of Pelagonemertes (PI. VIII. fig. 3), will 

 demonstrate this, and at the same time show it to possess the arrangement of muscular 

 layers and other peculiarities that are typical for Schizonemertea. These muscular layers 

 are, however, exceedingly reduced in thickness, and occupy a very inconsiderable fraction 

 of the vertical or horizontal diameter. The proboscidian sheath is, in the fragments 

 investigated, thin and unimportant ; in more posterior sections there are indications 

 of its place being taken by more irregularly shaped, cellular material, without a lumen. 

 I am, however, not satisfied with the details that could be gathered from these fragments 

 concerning these important morphological points, and must refrain from more particularly 

 insisting upon them. The transverse blood-vessels are exceedingly numerous and tor- 

 tuous — the latter phenomenon causing their lumen to be transversely cut a large number 

 of times in every section ; these apparent perforations of the gelatinous tissue giving a 

 very peculiar appearance to most of the sections. 



Another reason why I do not venture to establish a distinct species upon these 

 peculiar fragments, is the fact that I found them to be very considerably infested by a 

 large unicellular parasite (probably a Gregarine) which was not (as the Gregarines that 

 infest Nemertea generally are) found in the intestine, but which was present in consider- 

 able numbers in all the different tissues, both without and within the muscular layers. 

 When surrounded by gelatinous tissue, there was always a well-marked space round the 

 parasite in which it was contained. 



There was no distinct capsule, and the free space may perhaps not have existed 

 during the life of both host and parasite. When first noticed, these unicellular parasites, 

 with very distinct nuclei and granular protoplasm, might have been mistaken for ova ; 

 not only their distribution throughout the animal as isolated individuals, but also the 



