1904.] EARTHWORMS FROM NEW ZEALAND. 261 



the separation of Plutellus from these two genera, merely on 

 account of the presence of meganephridia only depends on a point 

 quite as small. 



I have already described a species of Plagiochceta, viz. PI. rossi, 

 in which micronephridia replace the meganephridia of the other 

 half-dozen species ; and embryology has taught us that the one is 

 ■derivable from the other condition — that, at any i-ate in the genera 

 MegasGolides (Vejdovsky) and Megascolex (Bourne), the earlier 

 meganephridium breaks up into numerous micronephridia. 



Is not the separation of the genera according to the condition 

 of the excretory system a remnant of my own unfortunate attempt 

 to classify the families of Earthworms into " Plectronephrica " 

 and " Meganephi'ica " ? 



But without entering upon the laborious task of essaying to 

 rearrange the " Cryptodi'iline " genera, I will express the opinion 

 that a careful study of the form and structure of the prostate 

 (together with other characters) may be more likely to lead us in 

 the right direction. And, firstly, it seems to me profitable to 

 distinguish the " tubular "-cylindrical prostate, such as occurs in 

 Ilegascolides amhicdis, from the flatter, elongated "tongue-shaped " 

 form of gland that occurs in Tokea, some species of Plutellus^ , and 

 others, and the "flattened, lobed, and compact" organ characteristic 

 of such genera as Pheretima and Ilegascolex. That these may 

 form a developmental series. Miss Sweet's work (1 900) has rendered 

 probable; but they also appear to have structural difierences 

 that may turn out to be of diagnostic character. At any rate, 

 they are easily recognised macroscopic characters ; whereas the 

 study of a worm from which the posteiior end has been acci- 

 dentally destroyed will not enable me to decide, in all cases, 

 whether it belongs to the genus Megascolides or to Notoscolex as 

 ■defined by Michaelsen. 



It is not difiicult to imagine the way in which the genus Tokea 

 has developed from an Acanthodriline stock, in which the cylin- 

 drical prostate, instead of being coiled compactly and confined to 

 its proper segment, has burst aw^ay from this limited position, and 

 elongating backwards has not only become flatter but has lost 

 somewdiat of its smooth external surface. Such a form of 

 " tongue- shaped " gland occurs in Notiodrilus aucklandicus, in 

 which each prostate extends through five or six segments. From 

 such a form Rhododrilus may have developed — the posterior 

 gland has disappeared, and the sperm-duct has shifted forwards 

 so as to open close to the anterior gland ; whereas in Tokea the 

 anterior gland appears to have gone, and the posterior gland to 

 have moved forwards to meet the sperm- duct and to open 

 externally in the 18th segment. 



* In looking throua;h the descriptions of new species of Australian worms 

 published by Spencer (Proc. Roj-. Soc. Victoria in 1892, 1895, and 1900), I find that 

 the only species that possess elongated " tongue-shaped " prostates (he calls them 

 " tubular," but the figures show them to be like those of my species) extending 

 through several segments belong to the meganephric genus Flutellus in Michaelsen's 



