1 ] 8 DR. J. STEPHENSON OX THE MORrHOLOGY, CLASSIFICATION, 



Class Cliaetopofla, MichaeLsen unites them wifcli the Hii'udiriea in 

 a new class, Cliteilata. " I consider the Hirudinea," says he, 

 '-'frankly as Lumbricnlidsp which have undergone special modifi- 

 cations in adaptation to a carnivorous habit of life." It might 

 be justifiable, lie thinks, to include the Leeches as a family of 

 Oligochfeta, though as we have seen he does not actually do this. 



The character of the Leeches which is of interest from the^ 

 point of view of the present paper is the Inrge number of testes. 

 Michaelsen has no difficulty in showing that, as in the case of 

 other peculiarities, this too is foreshadowed in the Oligochseta ; 

 for example, Lamprodrilus satyriscus, a Lumbriculid, has either 

 three or four pairs of testes- The position of the testes behind 

 the ovaries, however, offers greater difficulties; Michaelsen does' 

 not wish to assjime a sudden dislocation backwards of the testes, 

 in such a manner that they "hop over"' the ovaries. A trans- 

 lation of the testes backwards can, he thinks, only take place 

 through the intermediation of a stage in whicli the series of 

 gonads are hermnphrodite. Hermaphrodite gonads have often 

 been observed ; for example, in specimens which show an abnor- 

 mally large number of genital glands (" supernumerary gonads " 

 — such series may extend as far back as segm. xviii), tlie anterior 

 are often testes,- the middle ones hermaphrodite, and the posterior 

 ovaries; though Beddard in a U?-ocJueta {=Pontoscolex corethrurns) 

 found the hindmost gonads to be testes. 



It seenis to me, however, that such a condition as that described 

 tOooyq in Chcctogaster oricntalis fui'nishes, perhaps, a more likely 

 origin for the multiple testes of the Hirudinea. On such an 

 assumption there would be no necessity to invoke a series of 

 hermaphrodite supernumei-aiy gonads — a double abnormality 

 Avliere it occurs to-day— as a transitional stage. In Ghcetogasier 

 orientalis male cells are produced abundantly, in every sexunl' 

 individual, in the segments behind the ovaries ; a stricter locali- 

 ZEition would result in segmentally arranged testes. And the, 

 only cause which Ave can surmise to have been active in the case . 

 of Chcetogaster. orientalis — the adoption of carnivorous or para-' 

 sitic habits — must also have existed in the ancestors of the' 

 Leeches. 



References to Literature. 



1. Beddaed, F. E.— a Monograph of tlie Order of Oligoclu-cta. Oxford, 1895. 



2. MicHAEiiSEN, W. — Uber die IJeziehuiigen der Hirudiiicen zu den Oligocliiitcn. ' 



Mitth. Zool. Mus.''Hamburg, vol. x.xxvi. 1919, p. 131. 



3. Stephekson, J. — Descriptions of two frcsli- water Oligochajte worms from the 



Punjab. Rec. Ind. Mils., TvoLi. 1907. 



4. „ Sfcud:ies on the aquatic Oligochseta of the Punjab. Eec. Ind. ' 



Mus., vol. V. 1910. 



5. ,, On Intestinal Respiration in Annelids : with Considerations 



on the Origin and Evolution of the Vascular System in 

 that Group. Trans. Roj'. Soc. Edin., vol. xlix. pt. iii. 

 1913. 



6. Vejdovskt, p.— Sj'stem und Morphologic der Oligocliaten. Prag, 1884. 



