SMALLWOOD : MATUKATION OF HAMIXEA SOLITARIA. 263 



amount of material, I have been able to work out a fairly complete series 

 of the changes occurring in this period of development. 



Under natural conditions Haminea solitaria deposits eggs at any time 

 of day or night ; but many more were laid between three and six o'clock 

 in the morning than during all the rest of the twenty-four hours. In 

 confinement there did not seem to be any time that was especially favor- 

 able for egg-laying. Eggs were usually laid from eight to twelve hours 

 after copulation. My plan was to observe when copulation took place, 

 then to isolate the individual that was about to lay, and watch until the 

 process began. In this way I was able to secure a large number of eggs 

 in the early maturation stages. By killing a number of animals during 

 the process of deposition, a large amount of material was secured for 

 future study. 



It is practically impossible to determine the exact number of eggs in 

 a single capsule, the size of the capsules varying much, and the number 

 of the eggs being large. I should estimate that there were on the average 

 about two thousand eggs in a capsule. An animal can produce a single 

 capsule in forty-five minutes. When the capsule is finished, the eggs 

 first deposited are in the two-cell stage. One hour after the capsule has 

 been laid, all of the eggs are in the two- or four-cell stages, the develop- 

 ment being much more rapid than is usual in Mollusca. 



In general, the technique involved has been very simple. The ordi- 

 nary fixing reagents were tried. Kleinenberg's picro-sulphuric and 

 Conkliu's picro-acetic mixtures gave the best results ; the latter, being 

 much the more satisfactory, was exclusively used on the material de- 

 scribed in this paper. A whole capsule, when dropped into the fixing 

 fluid, even if left a long time in it, often failed to be penetrated. To 

 obviate this difiiculty, the capsules, after they were placed in the fixing 

 fluid, were cut up into small pieces with wooden needles, which could 

 be used without much danger of crushing the eggs. The eggs were left 

 in the fixing fluid for one hour, then placed in 70% alcohol, which was 

 frequently changed, where they remained until the color due to picric 

 acid was removed. The removal of the water from the albumen sur- 

 rounding the eggs causes the whole mass to stick together. This has a 

 certain advantage, for it allows the later treatment of the eggs in one 

 mass, instead of singly. There is a sti'ong tendency for particles of dirt 

 to adhere to the outside of the capsule ; this often renders cutting diffi- 

 cult by increasing the liability of the sections to tear. 



For staining, use was made of Heidenhain's iron-hfematoxylin, fol- 

 lowed by an aqueous solution of Bordeaux red as a plasma stain. This 



