CRANGON VULGARIS. 101 



the date at which the young appears in Vineyard Sound. 

 Speuce Bate (*76) states that in Crangon and several 

 other genera of shrimps, "he has demonstrated that the 

 three pairs of mobile appendages in the cirripedal or 

 Nauplius form of larva homologize with the eyes and two 

 pairs of antenna?, and not with the antennae and mandibles, 

 as stated by Fritz Miiller, Anton Dohrn, and others." It 

 is unnecessary to go into any detailed demonstration to 

 show that nothing of the sort really occurs. Kingsley 

 ('86 and J 86a) gives a brief account of the development 

 of the compound eye in this genus. 



METHODS. 



I was not very successful in keeping ray shrimps in 

 confinement, owing, doubtless, to insufficient means of 

 renewing the water. On this account I was obliged to 

 depend for my material on fresh specimens caught almost 

 daily, and to rely upon chance for the successive stages. 

 Many attempts were made to obtain the parents before 

 oviposition and to have them lay in confinement, but with- 

 out success. I made some observations upon the ovarian 

 egg, but they are not complete enough for publication. 



For surface views I studied the fresh egg, and in the 

 earlier stages I found it extremely useful to allow weak 

 alcohol to run under the cover glass while the eggs were 

 on the stage of the microscope. In this way parts before 

 invisible are rendered distinct, and, at a certain stage of 

 the process, the embryonic portions, when viewed by re- 

 flected light, are white upon a dark ground afforded by 

 the yolk ; by transmitted light, brown upon a translucent 

 surface. This effect soon vanished, and all portions, 

 when thoroughly impregnated with the alcohol, appeared 

 alike. Stained specimens, viewed as opaque objects, 

 were also of great value as may be seen from the plates. 



