EEPORT OiSI THE NEMERTEA. 93 



posterior brain -lobe, then, indeed, Caiinina may be said to represent — also with respect 

 to the fissures and grooves on the head — a stage of development in which both the 

 characteristic features of the Hoplonemertea and the Schizonemertea are still present in 

 combination. In deviating from the original arrangement, the Schizonemertea would 

 have gone a longer way than would the Hoplonemertea, some of wliich still answer to 

 the original type of structure found iu Ccmnina. 



I now wish to consider more closely certain details of these difi'erent cephalic fissures, 

 which cannot be discussed in a more appropriate place than in the section treating of 

 the sense-organs, although their exact significance must for the present remain unsolved. 

 In spirit preparations the ciliated coating of the body is generally never better preserved 

 than in these furrows ; and the cells carrying the cilia, as well as their nuclei, are in most 

 cases exceedingly distinct. However, in a few cases it is only the superficial layer of 

 the integument that is thus continued as a clothing of the inner surface of these furrows. 

 In most cases I could observe the deeper layer of integumentary glands (Schizonemertea) 

 to be continued, although less compact, along the whole inner surface of the cephalic slits. 

 Generally these deeper glandular layers appear to have undergone some special modifica- 

 tion in connection with the canal that opens out at the bottom of the furrow, and leads 

 into the brain-substance, a modification which may already be noticed in so primitive a 

 genus as Carinina, which, however, with respect to this apparatus, may be said to be 

 more differentiated than the allied genus Carinella. 



We find in Carinina (PI. VI. figs. 1-3) that all round the bottom of this groove {Cg) 

 there is a marked increase of the number of nuclei in the integumentary tissue ; and 

 although these nuclei can scarcely be said to belong to the layer of the deeper glands {cf. 

 PI. IV. fig. 1 E, and the paragraph on the integument), but rather to the one exterior to 

 this, the fact of their accumulation in this marked way, just along the inner surface of 

 the cephalic groove, is a most reliable indication that the integument is in some way 

 modified in adaptation to the significance of these grooves. In PI. VI. fig. 1 a distinctly 

 pointed shape is assumed by this wedge-like or horse-shoe-shaped accumulation of nuclei, 

 and a fibrous band connecting them with the intermuscular tissue is even visible, more or 

 less clearly, separating — at least in this section — a posterior brain-lobe -B?-', into which 

 the canal passes, from the anterior brain-mass Br {cf. woodcut, p. 81). The glandular 

 layer is, however, not indifi"erent or neutral during these changes in the exterior nuclear 

 one ; and although the two specimens at my disposal do not permit me to unravel the 

 whole of the modifications it undergoes, I may still be permitted to observe that in figs. 

 2 and 3 of PI. VI. its participation {Gi and gl.hr) cannot be denied, whereas a comparison of 

 all the three figures here given makes it appear very probable that these glandular elements 

 {gl.hr), derived from the deeper layer of the integument {Gi), play a part with respect 

 to the posterior brain-lobe of Carinina, which may best be compared to the glandular 

 investment of the posterior brain-lobe, as it is encountered in all the other Nemertea 



