38 KINGS LEY. [Vol. VII. 



derful to say, at least a dozen little fellows, all hatched this spring, 

 and all alive, had taken their place. With these were also at 

 least thirty eggs, in different, but all in advanced, stages of 

 incubation. In some of them the young could be plainly seen 

 revolving." Here was a retardation of development for almost 

 a year ! 



Methods. 



The observations here recorded were made at the Marine 

 Biological Laboratory at Woods Holl, Massachusetts, during 

 the months of June, July, and August, 1889 and 1890, and in the 

 zoological laboratory of the University of Nebraska. In writing 

 up the results obtained I have been hampered not a little by 

 my distance from the larger libraries, and hence the compara- 

 tive portion of the paper is sadly deficient — a fact which no one 

 can realize more than myself. 



For my material I have relied partly upon the natural nests 

 and partly upon artificial impregnation. With the former 

 method one cannot be certain of the age of his material, for not 

 infrequently two ovipositions become mixed. I have never suc- 

 ceeded in getting the crabs to oviposit naturally in confinement. 

 In artificial impregnation the eggs and milt were sometimes 

 obtained by squeezing individuals taken in copido, or by sucking 

 these products from the genital ducts with a pipette. Very 

 severe squeezing will force out but a small number of eggs, — far 

 fewer than are naturally laid in a nest, — while any attempt to 

 remove them from the body by cutting covers the eggs with a 

 layer of very rapidly coagulating blood ((inde Howell, '85), which 

 affords an excellent nidus for bacterial and fungoid growths. 



The study of the early stages has proved very difficult from 

 the fact that the eggs are the most refractory objects I have 

 ever seen. Until the outlining of the germ there is no means 

 of orientation, so that sections must be taken hap-hazard. The 

 greatest care must be taken in hardening them in order to pre- 

 vent the yolk becoming too hard for the section knife ; and after 

 numberless experiments with every reagent I could think of, I 

 came to rely almost entirely upon killing the eggs by heating 

 them in sea-water to 70°-^$° C. and then passing them through 

 successive grades of alcohol, from 30 per cent to 70 per cent, in 

 which they were finally kept. Eggs thus treated afforded at 



