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Part III. — Twenty-second Annual Report 



Eggs picked off the bottom alongside the spawning female had large 

 perivitelline spaces, with perfectly smooth chorion; there was no trace of 

 any sticky fluid outside the egg. 



The eggs which were displaced from the abdomen in transferring the 

 spawning female to a glass jar from the box in which it had previously been 

 kept lay on the bottom of the dish, and were with few exceptions 

 emptied out of the dish by gentle rinsing. The few which remained 

 attached to the glass were dislodged by the touch of a brush or with a 

 pipette. 



"When the pipette was crowded with eggs, and in one case where the 

 eggs were allowed to accumulate in a compact mass, on forcing them out 

 some remained sticking to the glass. These were the eggs which showed 

 the little prominences on the chorion mentioned above. On examining 

 the end of the pipette with the microscope, at nearly every egg a little 

 refractive globule was seen attached to the exterior of the chorion. 

 This is without doubt the perivitelline fluid which has been squeezed out 

 and which served to glue the egg to the glass in this case. 



In another case the eggs which lay on the bottom of the box were 

 found the next day to be stuck together in masses, which, however, readily 

 broke. The attachment of the eggs to one another was probably due to 

 the perivitelline fluid which the mutual pressure of the eggs would no 

 doubt tend to press out. A similar condition was observed in the case of 

 the unattached eggs of Cancer pagurus. After several days the eggs 

 which lay on the bottom of the box had become attached together in 

 masses. 



The Spawning of C. mamas. 



A crab which had just extruded its eggs on September 28th was sur- 

 rounded by a quantity of eggs which looked like red dust on the sand. 

 It was removed to a glass vessel and examined in water. It was 

 then seen that the abdomen of the crab was being held away from the 

 thorax and that it formed a kind of basin. The points of the 

 endopodites lay on the openings of the vulvae. A small quantity of eggs 

 were attached to each endopodite, and eggs were noticed in the openings of 

 each vagina. The endopodites were moved forwards, backwards, and 

 outwards, widely separated laterally, inwards, and forwards. The 

 independent movement of the distal part of the endopodite was seen. 

 The exopodites move a little in unison with the endopodites in certain of 

 the movements. 



The crab gradually threw ofT the eggs that were attached to the 

 endopodites. 



On the endopodites a similar condition to that seen in Cancer pagurus 

 was found. The chorion of the egg had been pierced by the hair and it 

 was in a collapsed condition. 



On October 16th a crab was examined which had spawned since 

 the previous day. The eggs on the endopodite showed their outer 

 envelopes (chorion) all wrinkled, but the yolk-sphere was not pushed to 

 the pole away from the hair: it lay simply in the middle of the irregularly 

 crinkled envelope. The stalk was not yet formed. 



A considerable number of dead eggs was found attached to the endo- 

 podites of a berried Carcinus (October 14th) which had just spawned in 

 the Laboratory. The inner or vitelline membrane had been ruptured and 

 the yolk-sphere was broken up. It is possible that the yolk sphere may 

 have been pierced by the endopodite hair, though other agencies may 

 have been the cause of their destruction. 



Spawning seems to be completed within 24 hours. 



