132 



CLASSIFICATION. 



Order. Sub-Orders, 



1 



ENOPLA 



Class Turbellaria. 1 



Families. Sub- Families. 



* Amphiporid^e 



'< 



Amphiporince 



Nemertinae . 



ANOPLA 



Line 



idte 



Carinellid^e 



{ 



Cephalothricid^e 



Genera. 



I. Amphiporus. 

 II. Tetrastemma. 



III. Prosorhochmus. 



IV. Nemertes. 



V. Lineus. 

 VI. Borlasia. 

 VII. Cerebratulus. 

 VIII. Micrura. 

 IX. Meckelia. 



X. Carinella. 

 XI. Valencinia. 



XII. Cephalothrix. 



The characters of the order Nemertinea may be concisely described as follows : — Worms 

 with more or less elongated, soft, ciliated bodies ; nervous system composed of two conspicuous 

 ganglia connected by a double commissure and two main lateral trunks ; digestive system a ciliated 

 canal with two apertures ; circulatory system consisting of a series of closed contractile vessels. 

 The proboscis forms the most typical organ in the group, is surrounded by a special muscular 

 sheath, within which it glides in a corpuscular fluid, and passes in front between the commis- 

 sures of the ganglia, while the digestive tract is placed inferiorly. Sexes separate in the majority, 

 oviparous or ovo-viviparous. 



The order may most naturally be divided into two great sub-orders, distinguished from 

 each other by the presence or absence of stylets in the proboscis or typical organ of the group ; 

 the former being called after Max Schultze (but with amended characters) Enopla, 2 and the latter 

 Anopla. 3 



The sub-order Enopla is characterised further by the globular and somewhat double nature 

 of the nerve-ganglia, and by the fact that the lateral nerve-trunks are placed within the proper 

 muscular walls of the body. The mouth, moreover, opens on the ventral surface of the snout in 

 front of the commissures of the ganglia. The blood-vessels are more differentiated than in the 

 Anopla. The young, so far as known, do not undergo any noteworthy metamorphosis in their 

 growth. 



In the Enopla there exist one great group and a subordinate one, which latter, however, 

 retains so many of the characters of the former that it conveniently forms a sub-family. In the 

 chief division (Amphiporin;e) of the family Amphiporld;e the animals have two muscular layers 

 in the body- wall, an external circular and an internal longitudinal ; the proboscis is composed of three 

 divisions, anterior, middle, and posterior, the former having in the typical species seven coats, viz. 

 external elastic, external longitudinal, reticulated, inner longitudinal, circular, basement and 



1 Turbella, a little bustle or turmoil, referring to the ciliated integument of the animals. 



2 ri and"07rXa, arms. s a an d"0-Xa, without arms. 



