764 FRANK E BEDDARD, 



"intermediate characters" may be the result of such fertile crossings. 

 In the collection of earthworms described in the present paper 

 was a Single example of a Perichceta, which shows in my opinion 

 internal evidence of being a hybrid between Perichceta rokugo and 

 (perhaps) P. sieholdi. These two species are of about the same size, 

 which would of course conduce toward a successful pairing; I give 

 the facts, however, for what they are worth. 



The worm shows in the first place a curious external asymmetry 

 similar in character to what I have before seen in an ÄllolobopJiora 

 foetida. The clitellum is unevenly developed on the two sides of the 

 body. On the right side it occupies the three usual Segments; but 

 on the left side it is pushed a segment further back involving Seg- 

 ments XV — XVII inclusive; this cau have nothing to do with the 

 hybrid character of the specimen, because in both species which I 

 believe to have been concerned in its productiou, the clitellum occupies 

 the three usual segments viz. XIV — XVI. Nor is there any internal 

 asymmetry appearing to have a relation to this. 



With regard to internal structure, the two species which I 

 presume to be the parents of the individual described here, agree in 

 the characters of the alimentary caual, vascular System, septa and 

 nephridia. In all these points the supposed hybrid shows no 

 divergencies. 



The ditferences between the two species Perichceta rokugo and 

 P. sieholdi are found in the spermatothecae, the sperm-sacs, the sperm- 

 ducts and the stalked capsulogenous glands of segment VIII. 



The spermatothecie of the supposed hybrid resemble those of 

 Perichceta rokugo; so too do the sperm-sacs. 



The stalked capsulogenous glands are absent from the Vlllth 

 segment but there is a mass of perfectly similar glands — 24 in 

 number — in the XVIIth and XVIlIth segments. This may perhaps 

 indicate that not P. sieholdi but some other species is one parent. 



The elferent ducts afford the principal ground upon which I base 

 the conclusion that this individual is a hybrid between Perichceta 

 rokugo and P. sieholdi, or a form closely allied to the last. On one 

 side of the body (the right) the vas deferens opens into a "prostate" 

 identical in its characters with that of Perichceta sieholdi; the external 

 orifice of this gland was perfectly obvious upon the exterior of the 

 body. On the other side there was no trace of any atrium or of its 

 glandulär appendage. The vas deferens opens some way behind the 

 XVIIIth segment; externally the aperture was invisible. On one 



