CONCLUSION. 219 



Into this abstract question, of course, I cannot 

 enter. The reader who would wish to know more of 

 the subject than I have faintly shadowed forth in this 

 chapter, may consult Steenstrup's Memoir, published 

 by the Ray Society; Dr. Reid's admirable papers in 

 the 'Magazine of Natural History' 2d series; Lewes' 

 'Sea-Side Studies;' and the learned works of Pro- 

 fessor Owen. 



MKDUS^K IN VAEIOCS STAGE8 OF DEVKLOPMEKT. 



