546 John Beard 



served material in whatever way prepared yielded but little result. 

 Larvae were prepared in ali sorts of ways for microscopie examiuation, 

 mounted whole and in sections. But the usuai result was disappoint- 

 ment. Hence the drawings of the development given are mostly from 

 the living- object, and only in the case of two are sections figured. The 

 above applies only to the segmentation and true larvai stages. 



My earlier attempts to effect artificial fecundation were, like 

 those of my predecessors , without result. And so in the earlier por- 

 tion of the research larvae had to be sought with great trouble, 

 and in few numbers in the glasses of sea-water in which Comatulae 

 with Myzostoììiidae had been placed. This was a very troublesome 

 and tedious proceeding especially as it was impossible to keep the 

 Comatulae alive in small glasses for any length of time. Stili it was 

 not uncrowned with success , for it yielded a tolerably complete picture 

 of the whole course of development, which served to control and 

 verify the later researches on segmenting eggs and larvae obtained 

 by artificial fecundation. To obtain naturally fertilised eggs the fol- 

 lowing method, provided Comatulae are very abundantly to be had, 

 yields very fair results. A number of Comatulae infested with large 

 full grown M. glahrum are taken , and the arms cut away not far from 

 the disc. The Comatulae with their Myzostomidae are then placed 

 in small deep glasses fiUed with sea-water , and a gentle current of 

 sea-water is allowed to flow thro' the upper part of the glass. Eggs are 

 laid pretty nearly every day , if not every day, and as these eggs are 

 specifìcally heavier than sea-water, they sink to the bottom. If after 

 oue day the Comatulae be placed in a fresh glass, the water in the first 

 glass will contain a number of segmenting eggs or larvae the age of 

 which is approximately known. These may be kept living 4 or 5 days 

 or even more, and examined at any stage. But by this method the eggs 

 obtained are not very numerous , and after the Comatulae bave been in 

 the glasses a few days they usually break up, and then the parasites die. 



Whenever it was desired to examine the larvae contained in a 

 glass, in the case of both naturally and artificially fertilised eggs, the 

 water was filtered down to a small bulk. In this way a number of lar- 

 vae could be obtained in a very small quantity of water at the bottom 

 of the filter. 



This laborious method of obtaining larvae was superseded in the 

 later portion of the work by the discovery of an easy method of obtain- 

 ing artificial fecundation. A number of full sized Myzostomidae are 

 removed carefully from their hosts, and placed in a small shallow glass. 



