THE CRAYFISH. 43 



FIG. XIX. The advanced Crayfish embryo, just prior to the first moult ; drawn after 

 removal from the swimmerets of its mother. 



The successive stages of the Crayfish development are figured and fully described in 

 Eathke (32) and Huxley (29). 



FIG. XX. An embryo Lobster, shortly after the appearance of its swimmerets. 

 Sars (35) has published excellent drawings of all the larval metamorphoses of this 

 animal. 



(Figs. XVII. to XX. were drawn under a two-inch objective.) 



FIG. XXI. The third abdominal and sixth thoracic appendages (the latter lettered ii.) 

 of the above, drawn to the same scale. A. 2. 



