396 Dr. 0. Burger on the 



of an outer longitudinal muscular layer, of the subepithelial 

 muscle-layers, and the formation of a muscular tissue at the 

 cephalic extremity, where, in the case of Carinella, we found 

 a parenchyma, which persists in the Enopla also. Moreover, 

 we find these forms provided with cephalic glands, not present 

 in Ca7"ineUa, and probably likewise absent in its allies. A 

 cephalic gland is characteristic also of the Enopla ; and with 

 regard to this group we may make the same observation as in 

 the case of that to which Eupoh'a, Cerebratulus, &c. belong, 

 viz. that the cephalic gland remains small in forms which, 

 judged by the development of their nervous system, sense- 

 organs, and cephalic grooves, must be regarded as the 

 higher, such as DrepanopJiorus and Amphiporus, as also 

 Cerehratulus and Langia ; but that in Tetrastemma, Prosade- 

 noporuSj and Oeonemerfes^ on the contrary, as in the more 

 primitive Eupolia^ it has undergone a colossal development. 



The musculature of the body-wall is precisely similar in 

 structure in the case of the first group, in which I unhesi- 

 tatingly include Ca7'inella, Carinina^ and Carinoma — I would 

 prefer not to come to any decision as to the position of Ceplia- 

 lothrix, although I am inclined to assign it to the first group 

 — and in that of the third, which embraces the Enopla, and 

 consists of a circular, a diagonal, and a longitudinal layer. 

 In the second group, which includes the remaining forms 

 unprovided with a stylet in the proboscis {Valencim'a, Eupolia^ 

 Ltneus, BorJasia, Cerehratulus, and Langta),we find that the 

 musculature of the body-wall consists of a longitudinal, 

 diagonal, circular, and longitudinal layer. The entirely 

 diiferent position of the diagonal muscular layer in Group II. 

 as compared with Groups I. and III. is most remarkable. 



We have recognized the inner circular muscle-layer of 

 Group I. as not belonging to the musculature of the body- 

 wall, and have homologized it with the dorso-ventral system 

 which appears in the metamerized forms of Groups II. and 

 III., and which we have derived from the circular layer in 

 question. 



None of the groups is without a system of radial muscles, 

 the tracts of which split up the layers of the body-wall, 

 dividing them into compartments. 



In its ciliated epithelium, the manifold gland-cells thereof, 

 and the development of the deeper system of gland-cells lying 

 beneath the basement-membrane, the integument of the 

 Nemertiiies exhibits an unmistakable resemblance to that of 

 the Turbellarians. 



The musculature of the body-Avall of the Rhabdoccela * 



* v. Graff, ' Monographie der Turbellarien. — I. Ebabdocalida,' 1882. 



