CHAP. VI.] 



ANNELIDS. 



163 



Perionyx excavatus. In this earthworm a very remarkable 

 series of variations has been observed by Becldard. The accompany- 

 ing table shews the varieties in number of spermatheca? and position 

 of the generative openings which were found. The spermathecae 

 are generally 4, and are placed in the 7th and 8th segment, but in 

 several specimens there were 8 and their position varied from the 

 6th to the 11th segment. In all the varieties, however, they were 

 in segments adjacent to each other. In four specimens the sper- 

 mathecse were in the 8th and 9th segment on the right side and in 

 the 9th and 10th on the left. In normal specimens the male pores 

 are 2, but individuals with 4 (and perhaps 6) were found. There 

 are generally 2 pairs of ovaries and oviducts. In Var. No. 11 an 

 additional ovary was found on the right-hand side in the 11th 

 segment and in Var. No. 10 there were three pairs of ovaries. 



Table of Variations seen in P. excavatus (from Beddard). 



Though the position of both varied greatly, the male pores 

 were always posterior to the female ones. 



In some specimens certain of the segments were only divided 

 from each other on one side of the body, being confluent on the 

 other. For example in Var. No. 14, segments 11 and 12 and also 

 segments 18 and 19 were only divided from each other on the left 

 side (cp. Nos. 88—91). 



Out of 430 individuals 15 variations in these structures were 

 seen; of 12 of these variations single specimens only were found, 

 but two specimens occurred with each of the other three forms oi 

 variation. In a single case a nephridium was found nearer to the 

 dorsal line in one segment than in the adjacent segment. Many 

 of the conditions here occurring as variations are found normally 



11—2 



