No. 447] BREEDING HABITS OF CRAYFISH. 175 



is in very small amount as compared with the amount priKhiccd 

 by one male or with the great mass of eggs to be fertili/cd, hut 

 the actual number of sperm cells is quite large and that thc\- aic 

 numerous enough to fertilize all the eggs seems certain though 

 not actually demonstrated. As a fact when females wcix' iso- 



males till eggs were laid these eggs dcwloped as if fcrtih/eiL 



other parts of the female than the aimuhis and if it wciv not 

 protected as in the annulus it is (hlhcult to sec liow it rould long 



cells. The laying of eggs, however, may not occur for some 

 weeks after union. 



Again, in one case in which the annulus was remoxed from 

 a female just before laying, the eggs were deposited with normal 

 secretions and habits and though the female was left undisturbed 

 for five days the eggs then appeared shrunken and abnormal, to 

 the naked eye. Twenty-four days later there was only a mass 

 of mouldy dead eggs left on the female. Though there were 

 some cases in which normal females lost most of their eggs 

 by death and fungus yet the above eggs were thought to be all 

 bad from an early date and^it is probable they were not fertilized, 

 in the absence of the annulus. 



On the whole the evidence seems strongly to fa\or the view 

 that the sperm received into the annulus in union is the sperm 

 which later fertilizes the eggs. In fact it is possible that sperm 

 taken in antumnal unions may be used for the eggs laid the fol- 

 lowing spring. Experiments to test this are not yet completed. 



Mortality.— crayfish kept in the laboratory were not 

 fed till after they had laid eggs ; then they ate meat, raw and 

 cookedf raw hen's eggs, an4 pieces of earth worms, as well as 

 Chara and Hydrodictyon. After sexual union many died and 

 it was found that the males died in larger numbers than did the 

 females : thus in one lot seventeen died within two weeks of 

 union in March, and thirteen of those were males and only four 

 females. In several cases the males died within a few hours 

 after union. 



Date of laying. — After union there is quite a long period 



