SPECIES OF THE GENUS AULODUlLUS. 945 



It is remarkable that the atrium here is situated far forwards, 

 and is followed by a convoluted tube of great length which is 

 enclosed in a thick covering of muscle fibres forming a structure 

 somewhat similar to that of the coelomic sac in Brancliiura and 

 Kaivmnuria. I have called the tube following the atrium and 

 enclosed in the coelomic sac the " atrial duct " and restricted the 

 term atrium to the anterior rounded portion into which the 

 prostate opens. The use of the muscle fibres forming the coelomic 

 sac, or better the muscular sac, is to evert the terminal part of 

 the atrial duct, which thus projects out of the " spermiducal 

 chamber " as a fairly long pseudo-penis. 



The term " spermiducal chamber " used by Goodrich in the 

 case of Vermiculus is retained here too, for a similar structure, 

 i. e. the ventral depression of the body-wall, into which the atrial 

 ducts open and the penial setse lie. 



The prostate gland as usual in the family is voluminous and 

 composed of cells, which when full of secretion become disorganized 

 and lose their cellular structure, the secx'etion being thus massed 

 together flows directly into the atrium. The prostate appears to 

 arise as a part of the atrial epithelium, which bursts out of the 

 atrium as a sort of hei-nia or outgrowth. 



The penial setal sacs are provided with masses of large pear- 

 shaped gland cells, which lie in the body-cavity outside the setal 

 sacs themselves though connected with their walls. 



I wish to express my wai-mest thanks to Mr. F. A. Potts 

 and Dr. J. Stephenson of Edinburgh for valuable suggestions in 

 connection with this work. 



(2) Diagnosis of the Genus and Species. 



The chief characters of ^wZoc^nZits are the following :■ — Dorsal 

 setse capilliform, uncinate or oar-shaped (with thin flattened 

 distal extremity) ; ventral setae uncinate. The uncinate setse 

 (crotchets) have the outer prong (the one on the outer side of the 

 cui-ve of the shaft) much smaller than the inner, or the outer 

 prong may be absent. The penial setae, of very difiei'ent form, 

 are the modified ventral setas of the 7th or 10th segment. The 

 atrium is small and subspherical ; it is followed by a long con- 

 voluted atrial duct, which is enclosed by a thick covering of 

 muscle fibres to form the "muscular" or "coelomic sac." The 

 terminal part of the atrial duct is capable of being evaginated to 

 form a long soft pseudo-penis. The sperm-sac is formed by the 

 backward extension of septum 6/7 or 9/10, and the ovisac by that of 

 septum 7/8 or 10/11. The clitellum occupies segments 7 and 8, or 

 10 and 11. The spermathecae lie in segment 6 or 9. The hearts 

 are in segment 6 or 8. Supra-intestinal, sub- intestinal, and 

 integumental capillar^'- networks are absent. The formation 

 of new segments takes place some distance in front of the anus. 

 Asexual reproduction by fission as in the ISTaididsg does not take 

 place. 



