2 THE VOYAGE OF H.M.S. C'HALLENGEE. 



systematist's point of view. Hardly any traces of coloration were visible, no external 

 appendages distinguished the different species, no definite sliape, marked out by hard 

 portions of the integument, which fiicilitate the recognition of representatives of so many 

 other divisions of the animal kingdom, were anywhere noticeable. 



The majority of the specimens in the collection were cylindrical or flattened fragments, 

 generally truncated, and rarely so intact that it was possible at first sight to distinguish 

 between head and tail. The cephalic slits of those specimens which belong to the group 

 of the Schizonemertea, and the mouths of many of the fragments, were the only external 

 marks that could serve both for the discernment of what was posterior and anterior, 

 and for a rough and provisional arrangement of the forms as they were probably related 

 to each other. 



The various figures on PI. I. will give a general impression of the appearance of the 

 frao-meuts just alluded to. I more especially insist upon the poor aspect presented by 

 the preserved material of the Nemertea in order to impress the reader with the fallacy 

 of pronouncing an unfavourable judgment on a collection of marine invertebrates hj 

 relyinw merely upon the external appearance of the specimens. For I can hardly 

 sufficiently emphasise the exceedingly good state of preservation of the large majority 

 of the Challenger Nemertea. They were, indeed, in so perfect a state that the 

 internal anatomy of all the fragments could be determined, and in very many cases 

 delicate histological details could be revealed with as much facility as if the specimens 

 had been captured a few days instead of ten years ago. I feel the more called upon to 

 make this statement, and to express my admiration for the extreme care which the 

 scientific staS" have so evidently given even to unattractive and small-sized fragments, 

 as it has been occasionally stated (even in certain of these Reports) that the Challenger 

 material was sometimes unfit for the minute investigation of internal anatomical struc- 

 tures. So fiir as the collection of Nemertea is concerned, this statement is absolutely 

 unfounded. 



The study of the fragments and complete worms constituting this collection was only 

 possible by aid of the microtome. This instrument was very freely made use of, and the 

 most important improvement to which it has been subjected by Caldwell, whose 

 automatic microtome was available, has enabled me to go into many more details than 

 would otherwise have been possible. The total number of sections through diflerent 

 specimens of the Challenger material which have been prepared in the drawing up of this 

 Report amounts to 19,560. They were all of them stained with Ranvier's picrocarmiue. 



As already mentioned in the Narrative of the Voyage,^ the number of Stations from 

 which the Challenger obtained Nemertea is more than twenty. It cannot be said that 

 any of the three large subdivisions of the group is limited to any special region of the 

 globe, although representatives of the very lowest and most primitive genera of Palseo- 



' Narr. Chall. Kxp., vol. i. pt. ii. p. 831, 1885. 



