114 Part III. — Titenhj -second Annual Report 



which was large and full. The eggs measured about '4 mm. in diameter. 

 Some were a little less ; others larger and narrower. Certain of the eggs 

 were put into fresh water : others into sea- water. They began to form 

 spaces in a few minutes. In the fresh water the eggs which had been of 

 a bright red colour imbibed the water so much that the inner egg (yolk- 

 sphere) became disorganised, and the fluid in the space became red or 

 amber-coloured. The whole egg, moreover, became whitish-pink to the 

 naked eye — the condition seen in dead eggs. A considerable peri- 

 vitelline space formed in the eggs in the sea-water in about ten minutes, 

 and the eggs were not disorganised. 



The rapidity with which the perivitelline space is formed depends on 

 the stage of development of the egg. Minute differences occur between 

 eggs of an apparently similar stage of ripeness. 



In another case the eggs were examined twenty minutes after they 

 were put into sea-water, and they then showed perivitelline spaces. 

 Several days afterwards, the perivitelline spaces had increased in extent, 

 but the eggs retained the fresh normal colour. 



In none of the experiments did any of the eggs stick to the glass. 



On October 30th a crab was found to have spawned, probably during 

 the preceding twenty-four hours. A large quantity of eggs was lying in a 

 heap on the bottom of the tank, while a large amount of eggs was 

 contained on the abdomen. Some of the hairs of one of the endopodites 

 were snipped off, and on examination the attached eggs showed an early 

 condition of the process of attachment. In some the zona was not yet 

 completely collapsed : some of the eggs were however already stalked. 

 There was a number of dead eggs attached to the hairs. On one of the 

 hairs the little cilia were seen to be turned back, as if they had been bent 

 over as the hair was pushed through the egg membrane. The eggs that 

 were lying on the bottom of the box were quite separate, and they showed 

 under the microscope no coating of cement, as did neither of the ovarian 

 or attached eggs. 



An experiment was made with the view of testing whether or not the 

 perivitelline fluid had adhesive properties :- this fluid was found to be 

 sticky. Some ripe eggs were put into sea-water and left there until the 

 perivitelline spaces were well developed. Four of these were transferred 

 to a watch-glass. The chorion of one egg was pierced by means of a 

 needle, and the egg began immediately to show an adhesive property. 

 Under the microscope a slightly refractive fluid was seen to have flowed 

 out of the puncture and to have stuck to the glass. On the following 

 day the egg was attached to the glass, while the others were freely 

 movable. It was, however, detached by a puff of sea-water from a 

 pipette, although it resisted gentle suction by the same instrument. 



The egg then having the large perivitelline space is pierced by and 

 skewered on to an endopodite-hair. The chorion collapses, and being 

 extremely delicate falls round the hair clinging to it. The perivitelline 

 fluid being somewhat sticky no doubt helps to glue the chorion to the 

 vitelline membrane, to other parts of the chorion, and to the hair. 



The eggs which escaped piercing, and which lay on the bottom of the 

 box, showed large perivitelline spaces : they grow dull in colour and die. 

 It is probable that the pressure set up within the chorion by the osmosis 

 is sufficient to cause the death of the egg, unless it is relieved by the 

 piercing of the membrane. 



In certain ovaries degenerating eggs were found. They were usually 

 of a dull pink colour, and their contents were disorganised. The ovaries 

 were sometimes full of these eggs, e.g., in some of the crabs kept in 

 confinement— spawning having in some way been prevented. 



