96 Mr. F. E. Beddard on Earthworms from 



Oligochseta. A portion of the vas deferens liiglily magnified 

 is shown in fig. 6 ; it consists of a single layer of ciliated 

 cuboid cells, e^ch containing a large nucleus ; in structure 

 it is precisely similar to that of other earthworms. I have 

 figured a portion to show that there has been no mistake 

 on my part in the identification of the vas deferens, which 

 diflfers in several points from the vas deferens of other 

 earthworms. These differences consist mainly in the fact that 

 it lies chiefly in the same segment as the testis, opening 

 between this segment and the next, and that there is 

 only a single vas deferens on either side of the body. 

 The figure to which I have referred illustrates this point ; it 

 represents the testicular segment seen from behind : T is the 

 large oval testis, v.d. the coiled vas deferens, and p the pro- 

 state, in common with which the vas deferens opens ; (b is the 

 oesophagus seen in section ,• D and ?/, the dorsal and ventral 

 blood-vessels respectively ; the transverse trunk or heart {v.s.) 

 which unites the two gives off a large vessel which presently 

 divides into two branches, one passing up to the testis, the 

 other supplying the prostate. 



Evidently therefore this earthworm, in the structure of the 

 male generative organs, assimilates very closely to the type 

 of structure characteristic of, though not always found in, 

 the Limicolous Oligocheeta. Where there is but a single vas 

 deferens on either side of the body, as in the Naidomorpha, 

 Cheetogastridse, Tubificidge, and Enchytrajidse, its external 

 aperture is situated in the segment following that which con- 

 tains the testes, so that the vasa deferentia like the nephridia 

 traverse two segments, the internal funnel being situated in 

 one and the external orifice in tlie next. 



In the example of Moniligaster Barwelli described above 

 the vas deferens is confined apparently to one segment ; but in 

 other specimens the testes themselves lie in two segments 

 (8 and 9), projecting through the mesentery, so that the in- 

 ternal funnel of the vas deferens, which is represented by the 

 outer tunic of the testis, in reality does traverse two segments. 

 Furthermore there is an agreement with many of the Limi- 

 colae in the forward position of the testes and male generative 

 opening. In earthworms there are invariably two pairs of 

 vasa deferentia, which may {Urochceta) or may not [Acantho- 

 drilus) become fused posteriorly into a single tube on either 

 side, and they traverse several segments (sometimes as many 

 as six) on their way to the exterior. There is evidently a 

 great difference from the disposition of the male organs of 

 Moniligaster Deshayesi. In Moniligaster Deshayesi the male 

 generative organs have a disposition which is, so far as is 



