1907.] NATURAL SCIENCES OF PHILADELPHIA. 131 



ing thence by amoeboid movement into the oogonial mass at some 

 distance from its posterior end. This is certainly an error and, I 

 believe, based on defective fixation. Von Malscn states that in his 

 studies on the oogenesis of Dinophilus he relied chiefly on sections 

 matle from material fixed in Kleinenberg's picro-sulphuric. This 

 fixative, as I have already stated in the section on tcchniciue, is unre- 

 liable, at least for the study of the morphology of Dinophilus conklini. 

 Sections made from material fixed in this fluid yield images which 

 could easily lead one to believe in a close connection between the 

 ovary and the alimentary canal, and at the outset I was myself inclined 

 to such a view. Better preserved material, however, has demonstrated 

 conclusively that no such close connection exists. Moreover, in D. 

 conklini the oogonial mass is commonly separated from the alimentary 

 canal by the large oocytes, thus effectively barring any communication 

 between the oogonia and the alimentary canal. 



A median generative pore — sperm duct or oviduct — situated on the 

 ventral side, near the posterior end of the body, has been seen in three 

 species of Dinophilus, namely, D. vorticoides (Schimkewitsch, 1895), 

 D. kcniatus (Harmer, lS89a), and D. apatris (Korschelt, 1882). In 

 the last-named species the oviduct was seen during life, but was not 

 found in preserved material. It is with regret I confess that so far I 

 have been unable to demonstrate an oviduct in D. conklini, although 

 a careful search for it has been made. That it exists there is scarcely 

 the slightest doubt. Weldon (1886) was also unable to discover the 

 genital opening in D. gigas, and has assumed that a rupture of the body 

 wall occurs on the maturing of the genital products, allowing the latter 

 to escape; this occurrence being accompanied by the degeneration and 

 death of the animals. Whether this be true of D. gigas or not, it is 

 probably not true of D. conklini — although this species, as does D. 

 gigas, rather suddenly disappears on the arrival of warm weather — 

 since von ^lalsen (1906) has shown that in D. apatris, a species very 

 similar to D. conklini, the egg-laying period is one of considerable 

 extent. 



7. Discussion and Conclusions. 



Metamerism. — In Dinophilus conklini, as in other members of the 

 gi'oup, there is a distinct and well-marked metamerism. This is 

 expressed by the body wall in its external divisions, its ciliated rings, 

 and its mucous glands; by the nervous system in its pairs of trunk 

 ganglia, and by the nephridia in their arrangement in five pairs. The 

 metamerism is that of the annelids, and expressed in the same terms. 



