No. 646] SHORTER ARTICLES AND DISCUSSION 477 



A Comparison with Other Forms 



The method used for rearing- sexually mature Plntynereis from 

 the fertilized egg has heen used to rear other worms through to 

 the adult stage: namely, Pectinariu ijouJdii, Diopatra, Nereis 

 li.mhata, and Chatoptcrus. In all eases the worms were reared 

 from eggs cut out of the females and inseminated in sea-water. 

 In no case were the worms kept beyond September 15 (from one 

 to three months). Though it is usually slated that artificial in- 

 semination of Diopatra eggs is not possible, every attempt made 

 by the writer in 1911, 1912, 1913, 1914^ and 19i:) was .sueees.sful. 

 There is one danger to avoid with these eggs— initiation of de- 

 velopment by mechanical shock. The worms reared from Di- 

 opatra eggs are if anything more hardy than those of Platy- 

 nereis. In 1913 1 reared Divpatra in a watch glass to a length of 

 four centimeters. 



Fectinaria goiddii are likewise readily reared from eggs in- 

 seminated in the laboratory. These eggs are extremely beautiful, 

 small, and almost wliolly transparent. They are easy to handle. 

 I have found them the best eggs in my experience for study 

 under high power (oil immersion lenses). 



The specimens used were from the Eel Pond and are normally 

 smaller than I'rctinaria found outside of Eel Pond. They are 

 infested witb a distonir and an interesting ciliate: the latter I did 

 not find in the larger >pecMniens (1911). This if it be generally 

 true, together with the size of the K.'l Pond speeimens makes an 

 interesting case from the point of view of ei-oloLiy. 



Among the shed spermatozoa of r>.'ti,Mri.i a.v many in bundles 

 that break up after a short time in tlie >,-a-w;iter. In addition 

 to these one can always get bundles of spermaToL-ytes, immature 

 sperm, etc., by puncturing the body wall. It is a very excellent 

 form to use for the study of cytoplasmic inclusions: it is pos- 

 sible to get the whole history of the sperm on one slide. 



opacitv. and yolk iiifliienr,' tin" ruM' wirh wliich the animals can 

 V)e reared under hdiorarory conditions. I found no correlation. 

 Tin... tlie e^-'o! I'lntnncnis is almost transparent; it measures 

 ISO L>()i) .V, ,v /s ei^g has more color and measures about 100 ,x. 

 Tin- S.r, ... ..-^ 'he hardest of all to carry through. The egg 

 of r<ri;>,„rni ^iiiall and almost wholly transparent. It is 

 readily reared. The Chatopterus egg lia> more color than that 

 of Nereis and is smaller. It i^ easier m rear rhan tlie egg of 

 Fectinari<i. The Diopatra egg is whnlly opaque: it is the largest 



