Anatomy and Histology of Nemertines . 395 
change, owing to the recognition of a metameric arrangement 
in certain organs in the middle and posterior portion of the 
body in some more highly organized Nemertines. 
To Hubrecht must be ascribed the honour of having 
demonstrated the existence of septa in the region of the intes- 
tinal caeca, instead of the uniform development of the gela- 
tinous matrix, the parenchyma, in which all the organs are 
imbedded. This indefatigable investigator of Nemertine 
anatomy was likewise unremitting in his insistence on the 
constant relations shown in the arrangement of intestinal 
cseca, septa, blood-vascular loops, and, lastly, even of the 
proboscis-sheath. 
The immediate object of all this was finally to sever the 
connexion between the Nemertines and the Turbellarians, 
and to enrol them among the Annulata. According to the 
old-established classification the Nemertines were completely 
merged in the Turbellarians, of which they were merely 
recognized as suborders. 
Hubrecht, however, did not stop at this, but sought to 
establish relations between Nemertines and Vertebrates. In 
this direction I cannot follow him. Far-reaching specula- 
tions are permissible and justifiable only after an exhaustive 
study of the embryology of the form in question ; and in this 
respect my work is completely wanting. 
Yet it has seemed to me that it may be interesting to com- 
pare the various systems of organs, as we have learnt to know 
them in the forms we have examined, with those of the 
Nemertine genera not treated of in these pages, casting at the 
same time a passing glance in the direction of the Turbel- 
larians and the Annelids. 
Nemertines one and all possess a ciliated ectoderm. This 
either carries the whole of the gland-cells of the integument, 
and in this case rests on an almost structureless layer of 
connective-tissue, a so-called basement-membrane, or a portion 
of the gland-cells sink into the connective tissue, and we get 
a cutis, which is often rich in muscle-fibres. The first of 
these conditions is met with in all forms having a stylet in 
the proboscis, the Enopla, as also in Garinella , and, according 
to Hubrecht, in Carinina , Carinoma , and probably, too, in 
Cephalothrix. We find that a double layer of gland-cells, 
on the other hand, is characteristic of Eupolia , Cerebratulus, 
and Langia ; but, from the works of MTntosh and Hubrecht, 
w 7 e may conclude that it is present in Valencinia , Lineus y and 
Borlasia also. 
The development of a cutis is manifestly followed by 
highly important changes, as exemplified in the appearance 
