164 



MERISTIC VARIATION. 



[part I. 



in other genera and species. 

 1886, p. 308, figs. 



Beddard, F. E., Proc. Zool. Soc, 





A 





_2 



A. 



5 

 j8 



_8_ 



12. 

 n_ 



12 



13 



11 

 15 



16 

 17 

 18 

 10 



20 





'^ 



\-v 





^ 











Fig. 25. Perionyx excavatus. Diagrams shewing some of the variations in 

 respect of the number and positions of the openings of the spermathecre and 

 generative pores. From Beddard, P. Z. S., 1886. 



Perionyx griinewaldi, Michaelsen. Normally a pair of male 

 genital pores on the 18th segment, and a single oviducal opening 

 for the two oviducts in the middle line of the 14th segment. 



107. In two specimens a different arrangement was found. One of 

 these had the oviducal opening in the 15th segment [position of male 

 openings not specified and presumably normal]. 



108. The other had two oviducal openings, one in the 13th and one 

 in the 14th segment [not stated whether these openings were median 

 or lateral, nor whether each of them was a double structure as of 

 course the normal female opening is]. In this specimen the male 

 openings also were placed anteriorly to their normal position, being 

 in the 17th segment. Michaelsen, Jahrb. d. Hamburg, wiss. Anstalt, 

 1891, viii., p. 34. 



Allurus. In Terricolse generally, the £ pores are on the 15th, 

 and the $ pores on the 14th, as in the common Earthworm. 



109. Allurus tetraedrus, a widely distributed form, has £ pores on 

 the 13th and $ pores on the 14th, the £ pores being thus in front of 

 the ^ pores as a specific character. Under the name Allurus dubius 

 Michaelsen described two specimens having the male pores on the 

 14th instead of on the 13th, and the £ pores on the 15th instead of 

 on the 14th, each being thus one segment in advance of its normal 

 place [backward Homceosis]. Michaelsen, W., Jahrb. Hamb. wiss. 

 Anst., 1890, vie, p. 7 ; see also Arch. f. Naturg., 1892, lviii., 

 p. 251. Compare No. 111. 



110. Besides these is a batch of 8 specimens of A. tetrdedrus, loc. un- 

 known, 6 specimens had both £ and $ pores in the 14th. Clitellum 

 began in 23rd, tuberc. pubert. in 24th. These specimens are thus 

 intermediate between A. hercynius, which has the pores as in Lum- 



