264 REPORT — 1851. 



siologist at once to perceive that the ivhole system is limited by M. Duges to 

 the glandular mass which is so readily observed about the anterior third of 

 the body, whereas in reality this only constitutes one segmental unit, more 

 developed only than those are repeated in every ring of the body. Moreover 

 those singular intromittent organs lodged within pyriform vesicles, now first 

 described, were wholly unknown to M. Duges, Nor was this anatomist aware 

 that in this worm the oi^ipassages open by means of a fimbriated, ciliated 

 extremity freely into the cavity of the peritoneum. 



Expounding the views of M. Duges, Mr. Rynier Jones observes*, "The 

 generative system of the Nais presents a somewhat difi'erent arrangement to 

 that which exists in the Earth-worm. The swollen part of the body, in which 

 the sexual organs are placed, occupies a space of from five or six rings, be- 

 ginning at the eleventh. On each side of the eleventh segment is a minute 

 transverse slit, communicating with a slightly flexuous canal, which terminates 

 in a transparent pyriform pouch or vesicle ; the latter contains a clear fluid, 

 in which minute vermiform bodies are seen to float, and most probably repre- 

 sent the testis. The twelfth segment likewise exhibits two openings, each 

 placed upon the centre of a little nipple ; these are the orifices leading to the 

 female portions of the sexual system. The ovaria are composed of four large, 

 and several smaller masses of a granular character, and from them proceed 

 long and tortuous oviducts, which just before their terminations at the lateral 

 openings become thick and granular. These animals most likely copulate 

 like the Earth-worms, and lay their eggs in a similar manner. We have 

 already seen in Lumhricus terrestris ova containing two yolks, and conse- 

 quently giving birth to two animals ; but in the Nais every egg produces ten 

 or twelve young ones ; or perhaps we ought rather to say, that what appears 

 to be a single egg is in fact merely a capsule enclosing distinct ova, from 

 which a numerous progeny arises. The manner in which these compounds 

 are formed is easily understood when we consider the structure of the oviduct 

 described above. The granular germs escape no doubt separately from the 

 ovaria, and remain distinct from each other, as they pass along the tortuous 

 canal whicii leads to the external opening ; but at length arriving at the 

 thick and glandular portion of the oviferous tube, several of them become 

 enclosed in a common investment secreted by the walls of the oviduct, and 

 are expelled from the body with the outward appearance of a simple egg." 

 This is the account of M. Duges with reference to the reproductive organs 

 of Nais fiiiformis. 



The author of this Report will now proceed to state the results of his own 

 examination, conducted at great cost of time and labour. 



Every Nais, in relation to this system, is identically constituted ; this worm 

 therefore, like the preceding, is androgynous. Every individual tovi at As the 

 latter end of tiie summer dies by the bisection of the body. It is not true, 

 as reported by Duges, and before him by Spallanzani, that the fragments into 

 which the body of each worm becomes resolved, is again reconstructed into 

 a perfect wliole. Although tlie sexual system exhibits a tendency to seg- 

 mental repetition, there devolves upon the large anterior portion described 

 by Duges a special function, which the rest cannot perform ; and, on the 

 contrary, a duty falls on the posterior segmental units of the system which 

 the anterior cannot discharge. It is consequently evident that neither of the 

 moieties into which the body is resolved during the crisis of the reproductive 

 season can be organically perfect. Such fragmentary organism is wanting 

 in elements paramountly essential to individuality. 



* Op. cit. p. 209. 



