312 MR. F. E. BEDDARD ON NEW OR [May 18, 



though there has never, to my knowledge, been described so great a 

 number of variations as I have been able to record in the present 

 communication. Dr. Horst ' has recorded a variation in the form 

 of tlie spermathecse of PerichcEta indica and in the caeca of 

 Peiichceta musica, and Perrier" in the spermathecaa of Perichceta 

 affinis. 



Fourthly, and lastly, the probability, suggested above, of the 

 occurrence of variations must not be left out of sight. 



Assuming it to be proved that an actual variation does occur in 

 the present species, it will be necessary in the next place to eliminate 

 those variations that are mere monstrosities, and that can hardly be 

 considered to have any importance. Such are the occasional doubling 

 of segments on one side of the body, as the variations Nos. 4, 12, and 

 14 ; these are comparable to such monstrosities among Vertebrata 

 as two-headed lambs, calves with five limbs, and so forth, which are 

 not in any sense reversions to an ancestral type, but are owing to 

 some accidental cause, such as defective or excessive nutrition. On 

 the other hand, the remaining variations are to my mind of some 

 importance. These will now be considered in some detail. 



It must be noted first of all that the variations occur in the 

 generative system, and it is precisely the modifications of this system 

 which have enabled systematists to classify the group. 



These variations affect all the parts of the generative system — the 

 clitellum, the ovaries and their ducts, the spermathecse, and the male 

 organs. 



I will commence with the clitellum. This organ and the relations 

 which it bears to the male generative apertures has enabled M. 

 Perrier to classify the whole group, after a fashion which is in the 

 main satisfactory, though open to objections in certain cases. I have 

 elsewhere urged that, in so far as it separates the Anticlitellians, i. e. 

 LvmLi-icus and its allies, from the remaining genera of Earthworms, 

 M. Perrier's system is by no means artificial, but bears out other 

 anatomical differences. To distinguish the Intra- and Postclitellians 

 from each other is not so easy a task : in the first place, we have genera 

 like Megascolex, whose affinities are clearly with Perkhceta, and which 

 yet possess Intraclitellian generative apertures ; in the second place, 

 we find that within the limits of a single genus, i. e. Acanthodrilus, 

 the male generative orifices vary in position, and may be either intra- 

 or post-clitellian. 



If the relations of the clitellum to the male generative apertures be 

 used for classificatory purposes, it appears to me necessary somewhat 

 to alter Perrier's definition, and to divide Earthworins into two 

 groups, according as to whether the clitellum is placed far forward, 

 and commences in front of the male generative orifices, or whether 

 i( is placed further back and commences behind the male generative 

 orifices. 



That there is really a connection between the clitellum and the 



^ Notes from the Leyden Museum, vol. v. \t. 182. 



^ Nouvelles Arch. &c. loc. cit. p. lUt). These facts are of course liable to the 

 same criticism as my own. 



