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, wliere, in the case of Cari'nella, we found 

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

 we find these forms provided with cephalic glands, not present 

 in Carinella, 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 EiqwUa^ Cerehratidus^ &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 Dreimnoplwrus and AmphiporuSj as also 

 Cerebratulus and Langia ; but that in Tetrastemma^ Prosade- 

 noporusy and Geonemertes, on the contrary, as in the more 

 primitive Eupollay 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 Carinella^ Carimna^ and Carinoma — I would 

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

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

 • — and in that of the third, which embraces the P^nopla, 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 ( Valencinia, Expolia, 

 Lineus, Borlasia, Cerehratulus, and Langia) j\*q find that the 

 musculature of the body-wall consists of a longitudinal, 

 diagonal, circular, and longitudinal layer. The entirely 

 different position of the diagonal muscular layer in Group 11. 

 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 

 Avhich 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 

 Ncmertines exhibits an immistakable resemblance to that of 

 the Turbcllarians. 



The musculature of the body-wall of the Ehabdoccela * 



* V. Graff, 'Monographie dcr Turbellarien. — I. Kbabdixwlida,' 1881?. 



