CHAP. VI.] 



ANNELIDS. 



159 



96. Diopatra neapolitana. In the middle of a specimen 35 cm. long 

 was an arrangement somewhat similar to the above. The part marked 



m 



Fig. 23. I. The case of Diopatra neapolitana (No. 96) from the side. II, the 

 same looking upon the parapodia. C I. C II, the two supernumerary cirri. 



III. The case of Hermodice carunculata No. 95. Cv, cirrus of ventral branch 

 of parapodium ; Cd. dorsal cirrus ; Cv. I, Cv. II, the two cirri borne on the super- 

 numerary parapodium. (After Cori.) 



V was cut off as shewn in Fig. 23, I., it bore a normal cirrus, and 

 the other part of the segment, marked b, bore two cirri and two 

 bunches of bristles. The figure does not indicate that there was any 

 relation of images between these two parts, but this would scarcely 

 appear in this case unless specially looked for. Described afresh from 

 Cori, C. J., I.e., p. 573, figs. 10 and 11. 



Tn considering the evidence as to Secondary Symmetries reference 

 to these cases will again be made. 



Generative organs of Earthworms 1 . 



The number and ordinal positions of the primary and accessory 

 generative organs and of their ducts differ in the several classifi- 

 catory groups of Earthworms. In the evolution of these forms it 

 may therefore be supposed that Variation in these respects has 

 occurred. To this subject the following evidence relates. The 

 difficulty which was mentioned in the case of Variation in ver- 

 tebras, that there is no clear distinction between Homoeotic and 

 strictly Meristic Variation, will here also be met, inasmuch as the 

 total number of segments in these forms is indeterminate ; but 



1 For information and references on this subject I am indebted to Mr F. E. 

 Beddard and Mr W. B. Benham. 



