NOTE ON THE KAELY LARVAE OF NEPHTHYS AND GLYCEKA. 165 



fourteen days no further development took place. I have to thank 

 Dr. Allen for providing me with pure cultures of Diatoms and other 

 Algae, but I was unable to find any food which the larv;c would eat. 

 Nothing is easier than the rearing of Serpulids in a laboratory, and 

 especially is this the case with regard to Fomatoccros, which is a hardy 

 shore form, found growing even at the mouths of drains. It breeds 

 naturally and in great profusion in the tanks at Naples, the young 

 worms settling down and forming their tubes without having any care 

 bestowed on them. But very few of the free-living Polychaetes have 

 been reared to a late stage. Chaetopterus is an example of one which 

 has been raised (Allen and Nelson 1) and Lillie (6) was successful with 

 Arciiicold. I have found it very easy to rear the larvie of Nereis 

 dumerilii, which are derived from yolky eggs, as far as thirty segments 

 or more. Quite otherwise, however, is it with those free-living 

 Polychaetes which have a pelagic larva. It would thus seem that it is 

 possible to rear from the egg such forms as the Serpulids, which have 

 a typical Trochophore, and those which have yolky eggs, but no method 

 has as yet been devised by which the majority of the errant forms can 

 be fed and raised. 



The egg of Glyccra is discoidal, and it does not swell up in sea- 

 water. It is granular, but comparatively transparent, with a lighter 

 coloured nucleus. The egg of NcphtJnjs is also flattened at the poles, 

 but is opaque. The cleavage is equal. 



Unlike the larva described by Claparede and Mecznikow (2), the 

 larva of JVephihi/s Homhergi is granular and so opaque as to render the 

 study of the internal organs in optical sections very difficult. Neither 

 in shape nor in transparency can it be called a typical trochophore. An 

 early stage is shown in Fig. 1. The upper hemisphere is more conical 



Fig. 1. — Larva of Nrphf/n/s. 2 days. 

 From the ventral aspect, br. p. — Brown pigment. 



and of smaller diameter than the lower, and is surmounted by an apical 

 patch of cilia. The mouth is situated mid-ventrally on the lower 

 hemisphere, and strong cilia can l)e seen working within it. Brown 



