On the Life-History and Development of the Genus Myzostoma. 547 



such as a watch-glass, along witli about two or three teasiioonfuls of 

 freshly filtered seawater ; the animals are then well teased with clean 

 needles, so that a great number of eggs and spermatozoa are obtained 

 in the seawater. The mixture of pieces of Myzostomidae Is well stirred 

 up and allowed to stand for two or three hours. Then the pieces of My- 

 zostomidae are picked out with needles, and the water with its contained 

 eggs thrown into a glass full of freshly filtered seawater. This glass is 

 covered, and placed under the Andres air-apparatus, by which meaus 

 a gentle current of air can be passed through it, and the water kept 

 well aerated. 



Development then goes on and the larvae may be examined at any 

 stage. It is easy to get them to develop for fi ve or six days , but 

 beyond that the usuai well-known result ensues — most of the larvae 

 die. It is well to renew the seawater every second or third day. This 

 is easily effected. The minute larvae always remain at the bottom, and 

 thus allow of the pouring away of the greater portion of the water. and 

 so of its renewal. 



It is necessary to take at least four or five Myzostomidae in eaeh 

 experiment, for as the animals are hermaphrodite, self-fertilisation must 

 be as far as possible avoided. The number of instances in which it can 

 occur is, of course, very much diminished by increasing the number of 

 individuai Myzostomidae used in each experiment. 



For the investigation of the later stages of the development — that 

 is of the post-larval stages — the Comatulae were slowly killed in the 

 well-known mixture of alcohol and seawater. The Comatulae were 

 placed in a vessel containing a mixture of seawater with ten per cent Al- 

 cohol. When dead they were individually seized with forceps, and well 

 shaken in the mixture. The small Myzostomidae of both species, and 

 also the full grown M. cirrifenim are thus shaken off in great numbers, 

 and fall to the bottom. The superabundant water is poured off, and al- 

 cohol is gradually added until the animals lie in 90 "/o Alcohol. A great 

 number may be then stained together and mounted for microscopie exa- 

 mination. 



In the following portion of the work I have divided my subject 

 under three heads, viz. Anatomy, Development, and sectiou on the 

 males of M. glabrum. 



36^ 



