308 NEREIS DUMERILII. 



cirrus is shorter and devoid of the inferior papillae. The bristles become few and long, 

 but have the same structure. 



Those captured in the pelagic condition at Barra were nearly uniform in size, viz., 

 about 2 ins. in spirit. The vent is remarkably papillose. 



A small example (about 1 in. in spirit) from the Mediterranean has very large eyes 

 which are completely connate. The anterior region of the body has twenty-one segments 

 of the ordinary structure. The rest are heteronereid. It probably is a male though the 

 sexual elements are absent. 



The males of this form seem to be more frequently met with than the females at St. 

 Andrews — generally in March, and some reach fully 4 ins. If this is the male epitokous 

 form of N. Damer Mi the radical change in the structure of the first foot is interesting. 



In what appeared to be a small male from Plymouth the swimming lamellae occur 

 on the seventeenth foot, the thirteen anterior being large, and the fourteenth, fifteenth, 

 and sixteenth smaller and more compressed, but having no foliaceous development or 

 swimming bristles. The change is thus sudden. The eyes are large and connate and the 

 anterior pair have lenses. The paragnathi are well developed. 



The forms under which this species appears are : (1) The ordinary typical form 

 which produces ova and sperms in separate individuals without change in the feet. 

 (2) The same producing ova and sperms in the same individual. (3) The Iphinereis 

 transformation with swimming lamellae and bristles, and of separate sexes. 



In a small specimen, probably about an inch when living or very little more, the 

 eyes were as large as in the foregoing, and connate. There were fourteen feet of the 

 ordinary form in front, the next were heteronereid. It came from Jersey (Mr. Horn ell). 

 Posteriorly the heteronereid condition abruptly ceased, and about a dozen of the terminal 

 segments were of the ordinary form. 



Reproduction. — At Naples Lo Bianco l found this annelid mature in August, and the 

 larvae in the tube from December to February and April to August. The Heteronereid 

 condition occurred as a pelagic form from November to May. 



A young example of Nereis Ihmerilii captured in the tow-net by Mrs. Collings of 

 Sark in July has thirty-seven feet. The jaws have eight or nine teeth. The anterior 

 pair of eyes have lenses and are considerably larger than the posterior. They are trans- 

 versely ovate, whereas the posterior pair are irregularly rounded. This may be an early 

 example hatched the same season. 



In a small example of fifty-six segments, and measuring little over half an inch in 

 spirit, the eyes are considerably enlarged, and the dorsal cirri of the first seven segments 

 form large clavate processes with the filiform tip. It seems to be a very small male. No 

 change in the lobes of the feet or in the bristles have occurred. It was dredged in Tangiers 

 Bay in thirty fathoms by the ' Porcupine ' in 1870. 



An interesting account of the earlier stages in the development of this species at 

 Madeira is given by Langerhans (1879). He only found one out of several hundred examples 

 in the Heteroneveis condition. The eggs are whitish with a greenish point. The youngest 

 larva he examined had three bristled segments, with a single dorsal and several ventral 



1 The recent loss of this able observer at the Zoological Station, Naples, is to be deplored both 

 in the interests of science and of the workers there. 



