Structure of the Oligochceta. 91 



recognizable though very rudimentary) ; they commence in 

 segment 3. 



The second character in which Ocnerodrilus resembles the 

 Microdrili is the large size of the ova ; they are not, how- 

 ever, so large as in Phreoryctes, Enchytrceus, &c., but con- 

 siderably larger than in any earthworm known to me. 



Ocnerodrilus has no gizzard ; it has septal glands ; the 

 atrium is lined by a single layer of cells as in the Microdrili 

 and Moniligaster. It is clear, therefore, that the only 

 characters distinguishing the Microdrili from the Megadrili are 

 Nos. 1 and 2 of the list given above. 



It is a question whether they are sufficient, in view of 

 important points of agreement, to distinguish two such groups. 

 I am inclined, for the present at least, to think not, and to 

 revert to Vejdovsky's arrangement into families. 



In discussing the affinities of any particular type of 

 Oligochaet it is therefore necessary to compare it with a par- 

 ticular family and not to be content with indicating resem- 

 blances to the aquatic Oligochasta or to the terrestrial 

 Oligochasta as a whole. 



I have lately received from New Zealand, through the 

 kindness of Mr. W. Smith of Ashburton, a number of 

 examples of an Annelid which were collected in wet soil not 

 far from the margin of a swamp. 



I am uncertain whether to refer it to the Lumbriculidaj or 

 Phreoryctidaa ; it forms in any case a new generic type for 

 which I propose the name of Pelodrilus. 



I have referred above to Vejdovsky's discovery that in the 

 sexually mature Lumbriculus the genital segments contain 

 nephridia ; although this one exception is sufficient to prove 

 that the absence or presence of nephridia in the genital region 

 is not a character of first-rate classificatory significance, the 

 fact that Pelodrilus agrees with Lumbriculus is a further 

 proof that the Lumbriculida? and Phreoryctidaa stand nearest 

 to some of the simpler forms of Earthworms. I am not certain 

 as to Lumbriculus, but in Pelodrilus there is no vascular plexus 

 upon the nephridia. I have shown elsewhere (" On the 

 Anatomy, Histology, and Affinities of Phreoryctes" Trans. 

 Roy. Soc. Edinburgh, vol. xxxv. (1889), pt. ii. No. 16) that 

 the gonads and their ducts in Phreoryctes are extremely simple 

 in structure, and that the male gonads and ducts correspond 

 more closely than is the rule with the female gonads and 

 ducts. In these particulars they resemble the gonads and 

 ducts of the young Acanthodrilus just escaped from the 

 cocoon. In Pelodrilus the gonads lie in segments 10, 11, and 



