2$$ MR FRANK E. BEDDARD 



from the neighbourhood of the Tubificidse and brings it nearer to the Lumbriculidse, 

 or the Naidomorpha and some of the lowest groups. 



The presence of a diverticulum of the vas deferens is a perfectly unique character 

 among the Oligochasta. I am inclined to suspect that it may serve as a sperm reservoir ; 

 but this is only conjecture, as no trace of spermatozoa were discovered in the tube. 



The fact that this diverticulum is connected with the vas deferens suggests that it 

 may be possibly the representative of the second vas deferens, present in the Lumbriculidse 

 and most Earthworms, converted to another function. 



In some Oligochaeta, for example in Perichceta, Pontodrilus, &c, the atrium is a 

 diverticulum of the vas deferens, but there can be no question of any such condition in 

 Phreodrilus, since a structure evidently corresponding to the atrium is present in addition 

 to this diverticulum. 



The coiling of the diverticulum is just as striking as the coiling of the vas deferens, 

 but it does not extend into the following segment as the second vas deferens of a 

 Lumbriculid would. However, Sutroa, which is clearly a member of the latter group, 

 though a somewhat aberrant one, has two pairs of vasa deferentia, which all open into 

 the same segment. 



This interpretation of the diverticulum acquires a fresh significance when its resem- 

 blance in structure to the spermathecse is borne in mind ; a separation from the vas 

 deferens and the acquirement of an independent opening would result in the formation of 

 a structure which would be undoubtedly regarded as a spermatheca. There is not, how- 

 ever, at present any Oligochset known in which the spermatheca opens into the same 

 segment as the atrium. 



The development of spermathecse as appendages of the male and female ducts seems to 

 be a reasonable conception of their origin, but a great many more facts are required before 

 they can be satisfactorily connected with these ducts. In the meantime I would again 

 emphasise the peculiarities of the vasa deferentia in Phreodrilus, which seem to offer a 

 hint that this is the direction in which the explanation of the origin of the spermatheca is 

 to be sought. 



One of the most remarkable features about the atrium is the development of a special 

 sac round the junction of the atrium and the vas deferens, including the greater part of 

 both tubes. The structure in question does not appear to me to be a ccelomic sac, but 

 simply a space caused by the separation of the muscular wall from the atrium, which has 

 then undergone an increase in length resulting in the coiling of the tube within the 

 muscular sac. Apart from Eclipidrilus, which I have already mentioned, there is no 

 other Oligochset which shows anything analogous to this very extraordinary state of 

 affairs. If my interpretation of the nature of the circumatrial sac be correct, it is clear 

 that there are no grounds for comparing it with the ccelomic spaces surrounding the 

 genitalia in certain Eudrilids, notably in Hyperiodrilus and Heliodrilus [Beddard, 11]. 

 For in these cases there can be no doubt whatever that the sacs which enclose the sper- 

 matheese and other organs are ccelomic spaces which have been differentiated round them. 



