233 



The tact that among the nephridiopores that are situated above 

 the outer couple of setae a doublé arraugement is yet detected, 

 in the one case the nephridiopore piercing the integuraent close 

 above the fourth seta, in the other half way up the dorsal 

 surface, would even seem to favour the suggestiou that the ori- 

 ginal number of large nephridia has been three pairs. 



I do not wish to do any more than indicate a similar hypo- 

 thesis, leaving it for the more competent specialists to test it in 

 the different genera. As early as 1865 Ray Lankester (Quarterly 

 Journal of Microscopical Science, vol. V, 1865) suggests the 

 possible functional change by -which nephridia might be adapted 

 tö the service of the generative system (efferent canals , oviducts 

 and spermathecae) and consequently the possible archaic mulfci- 

 plicity of nephridia in each segment (functionally retained in cer- 

 tain living genera , e. g. Brachydrilus). What has been adduced in 

 this paper appears to be a new argument in favour of these views. 



EXPLANA.TION OF PLATE XII. 



Fig. 1. Lateral view of the anterior segments of an eartbworm (enlarged). 



SS', the row of the upper (4th & 3^^) setae. 



m. male genital pore. 



Cl. clitellum. 



Np. The dorsally placed nephridiopores , seventeen of which are 



visible. 

 » 2. Diagrammatic tranaverse aection of an earthworm. 



1. the intestine with the typhlosole /. 



nc. the nervecord. 



N. the nephridia, with Nd. the ducts and Np., the nephridiopores. 



The position of the left nephridiopore corresponds to what was 



indicated in fig. 1. 

 » 3. A dorso-lateral nephridiopore Np. more considerably enlarged. 



Nd. the nephridial duet, (with an exceedingly flattened epithelial 



16 



