474 FRANK E. BEDDARD. 



worms as Diachaeta aud Deodriius, in which there is no 

 prostomium, and in which, therefore, such an inversion will 

 cause no external change of importance. 



In worms which have a prostomium this structure may be 

 prolonged backwards, so as to commence as an outgrowth of 

 the 2nd segment ; if, in such a case, the peristomial segment 

 were permanently invaginated the prostomium would be left 

 attached to the 1st segment of the body, i. e. in the more usual 

 position ; on the other hand, a permanent eversion of the com- 

 mencement of the buccal cavity in a worm in which the 

 prostomium arises from the anterior margin of the peristomial 

 segment would lead to the apparent prolongation of the pro- 

 stomium back to the 2nd segment. 



§ Reproductive Organs. 



I have not found the testes nor the ovaries and oviducts. 

 Two pairs of sperm-sacs were to be seen attached to the an- 

 terior wall of the 10th and 11th segments; these organs are 

 racemose in form, as in so many genera. 



The vas deferens funnels appear also to be limited to a 

 single pair, which open into the 11th segment. 



The atrium, or prostate gland, is a compact flattened body 

 on each side of the body connected by a short muscular duct with 

 the male pore; it lies in the 18th segment. The atrium appears 

 to be branched, and to resemble the same organ in P e r i c h ae t a. 



Connected also with the male reproductive apertures is on 

 either side a thin-walled sac filled with penial setae. Two of 

 these setae are shown in figs. 15, 16 ; it will be seen from 

 an inspection of those figures that the form of the two setae 

 selected for illustration differs very considerably. In one the 

 distal extremity is covered with numerous minute points like 

 those which cover the distal half of the ordinary seta. In the 

 other seta these points are entirely absent, and fine wavy lines 

 are found on the distal part of the seta, ceasing, however, some 

 little way in front of the extremity. 



I call particular attention to the fact that two such different 

 forms of penial setae are met with in the same individual, iuas- 



