256 ANIMAL BIOLOGY. [Part II. 



tips are incurved. The dactylopodites of the third and fourth 

 pairs of legs are hooked. The appendages of the first abdominal 

 somite are undeveloped. Those of the last are enclosed 

 within the telson. It is probably set free at the first ecdysis. 

 Thus, as we found to be the case in the vertebrate, after trans- 

 formation is over there still is development. 



The student should endeavour to obtain, in the spring 

 or early summer, a female crayfish with developing embryos. 

 He will find a study of the development of their external 

 features a matter of no great difficulty and of very great 

 interest. 



