REPORT ON THE NEMERTEA. 59 



thickness of the layers, aljove described as integument, does not vary very much in smaller 

 and larger-sized individuals. Also, in the tip of the tail, where growth is continually 

 going on, and where the newly formed parts are thus, in the first instance, found, the 

 integument is very much in advance of the underlying tissues in obtaining its definite 

 size. For example, in Drepanophonis lankesteri I find the cellular integumentary layer 

 (the basement membrane not included) to be on the thickest part of the body, 0'15 mm. 

 (i.e., one-twentieth the horizontal diameter in this region), and close to the tail end O'l 

 mm. {i.e., one-tenth the horizontal diameter in this region). In the largest specimens of 

 Am'phiporus moseleyi, which have more than twice the length and more than two and a 

 half times the transverse diameter of Drepanophorus lankesteri, I find the integument 

 to measure 0"12 to 0"15 mm. 



Both in specimens of Amphiporus moseleyi and in one of Ampkiporus marioni, as 

 well as in one of Drepanophorus, it is easy to demonstrate glands in the integument by 

 the evident presence of the secretion, partly extruding towards the exterior, partly still 

 enclosed between the deeper layers (PL X. fig. 2). These glands are, however, neither so 

 massive, nor do they form such a conspicuous layer as in Carinina, above described. 

 Whether they may be regarded as unicellular, and as comparable to the superficial ones 

 already mentioned in the integument of Eupolia, and also present in the Schizonemertea, 

 or whether they are more directly homologous to the deeper glands of that division, 

 is for the present difficult to decide by means of the preserved material in the Challenger 

 collection. Histological investigation of fresh specimens will be necessary to clear up 

 this point. Drepanophorus serraticollis would certainly tend to a direct comparison 

 with the flask glands of Cerebratulus, &c. In a general way, however, the Hoplone- 

 mertean integument ofi'ers more analogy to the more primitive arrangement than to the 

 higher differentiation of the layers in Eupolia and the Schizonemertea. 



One further detail deserving mention is the presence of a granular deposit (pigment?) 

 in the lower ceU-strata of the integument of the last mentioned specimen of Drepano- 

 phorus. This deposit is diS"erent from the one hereafter to be mentioned in the tissues of 

 Amphiporus marioni. A deposit comparable to the latter was absent in the specimen 

 of Drepanophorus here alluded to. The granules have more resemblance to the pigment 

 granules of Eupolia delineata, described above, and may probably be looked upon as such. 



While we see that the Hoplonemertean integument is directly connected — at least in 

 general outlines — with that of the Palteonemertean genera Carinina and its allies, the 

 Schizonemertea are linked to the primitive stock by the intervention of Eupolia and 

 Carinoma. 



Certain Schizonemertea {e.g., Cerebratulus corrugatus) in some portions of the 

 integument reveal a complete uniformity with what we have described for Eupolia ; a 

 stratified basement layer separating the outer longitudinal muscle-bundles of the body- 

 wall from the layer of vesicular tissue sustaining the deeper skin glands, these glands 



