982 SUMMARY OF CURRENT RESEARCHES RELATING TO 



valve as it is in Lumbrirus. The structure of the nephridial tubule and 

 the shape, of the funnel calls to mind the common earth worm. 



Diachseta Thomasii g. et sp. n. is from St. Thomas, W.I., and has 

 the set® all simple and not bifid as in Urochseta; excepting the most 

 ventral they alternate as in Pontoscolex and Geogenia. Trigaster 

 Lankesteri is another new genus and species from St. Thomas, which is 

 remarkable externally for a deep median ventral fossa in the anterior 

 region of the clitellum ; it is bounded by two papillae, and is doubtless 

 used in copulation. It has three distinct gizzards separated from one 

 another by oesophageal regions. The author concludes with some re- 

 marks on the genera established by Kinberg, and on recent additions 

 to the literature of earthworms. 



Variations in Perionyx excavatus.* — From an examination of 

 more than 400 specimens of this earthworm, Mr. F. E. Beddard has 

 noted a number of variations in respect of the position and number of 

 the genital pores corresponding to a similar variation of the internal 

 genital organs, and accompanied by a shifting of the clitellum. 

 Amongst the fifteen variations, for instance, in one specimen the whole 

 series of pores is carried forward one or more segmeuts, as is also the 

 clitellum, which has the normal number of segments composing it. 

 In other cases the pores are further back than in the normal worm ; 

 in several cases the female pore, which is normally single and 

 median, is paired, and in other cases the median pore is repeated 

 in two segments. In one specimen there are four male pores, as is 

 usual in Acanthodrilus, and both pairs lie in segments anterior to the 

 normal position of the single pair of male pores. The spermathecae 

 are also sometimes reduplicated, being four on each side, instead of 

 two. 



The author considers these to be varietal and not specific 

 differences from the following facts: — (1) The exact correspondence 

 in size and colour, and in all other anatomical characters, except these 

 genital organs. (2) The fifteen variations are represented by only a 

 few specimens, only three being found in more than one specimen. 

 (3) Earthworms are known to vary somewhat in structure, e. g. 

 PericJiseta inclica ; and (4) the probability of the occurrence of 

 valuations. 



It is noteworthy that the variat'ons occur in the very series of 

 organs which are used to divide up the LumbricidaB. 



The author points out that Terrier's division of the group must 

 be modified, and that we must distinguish only two groups, according 

 to whether the clitellum commences in front of the male pore, or 

 behind it. 



Variation in other organs was not observed, except in the case of 

 the nephridia ; in one specimen one of the nephridiopores was found 

 to be displaced dorsally. 



Anatomy of the Naidomorpha.f — Herr A. Stole has some notes 

 on the entire vascular system of Nais elhujuis and N. barbata. In their 



* Proc. Zool. 8oc. Lond.. 1886, pp. 308-14 (4 figs.), 

 t Zool. Anzeig., is. (188G) pp. 502~b\ 



