CRANGON VULGARIS. 101 



the date at which the yoimg appears in Vineyard Sound. 

 Spence Bäte ('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 

 N'auplius form of larva homologize with the eyes and two 

 pairs of antennse, and not with the antennge and mandibles, 

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

 is mmecessary to go into any detail ed demonstration to 

 show that nothing of the sort really occurs. Kingsley 

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

 of the Compound eye in this genus. 



METHODS. 



I was not very successful in keeping my shrimps in 

 coniinement, owing, doubtless, to insufficient means of 

 renewing the water. On this account I Avas 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 themlay in confinement, but with- 

 out success. I made some observations upon the ovarian 

 Qgg>, 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 eoo^s were 



O CO 



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- 

 Üected light, are white upon a dark ground afforded by 

 the yolk ; by transmitted light, brown upon a translucent 

 surface. This eifect soon vanished, and all portions, 

 when thoroughly impregnated with the alcohol, appeared 

 alike. Stained specimens, viewed as opaque objects, 

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



