390 Problems /of Zcokgisis. [May, 



have not been found in the eggs of insects and Crustacea, but our 

 information on this point is still of a negative character, and new 

 and careful investigation may conclusively show that the Arthro- 

 poda in this respect do not form an exception to the rule that the 

 extrusion of polar globules is one of the features of the matura- 

 tion of the eggs of all animals. 



Grobben when studying the development of a small fresh-water 

 crustacean (Moina), found that certain cells, which eventually 

 formed the genital organs, were differentiated at nearly the same 

 time as the epiblast and hypoblast. Metchnikow has also found 

 in an insect that the reproductive organs were very early de- 

 veloped. When we consider that the chief end and purpose of 

 every animal is the reproduction of its kind, this early appearance 

 of the genital organs is what should be expected, but as yet, so 

 far as I am aware, these two observations stand alone. Here is 

 possibly a fruitful field for some ardent student. 



In the waters of the whole eastern United States (with the ex- 

 ception of New England), and the Mississippi basin, are to be 

 found representatives of a family of Mollusca peculiar to the 

 American continent, the Strepomatidse (Melanians). Of this 

 family numerous genera and many hundred nominal species have 

 been described, but as yet we know nothing of their embryology 

 and but little of their anatomy. With the exception of a paper on 

 the structure of two genera by the late Dr. Stimpson, a few short 

 notes is the sum total of our knowledge of true " soft parts." We 

 cordially commend the investigation of the " Melanians " to the 

 naturalists of the Mississippi basin. 



The fauna of the United States is exceedingly rich in Urodelous 

 Batrachia, and a fine field is open for a comparative study of their 

 visceral anatomy and their myology. Their osteology, however, 

 has been pretty carefully studied, though the results are not yet 

 published in full. European embryologists have confined their 

 studies of the development of the Batrachia to the tailless forms, 

 while Dr. Clark is the only American who has contributed any- 

 thing of any extent to our knowledge of the life history of the 

 salamander, 1 and his observations are principally on the external 



The calf fish ( Amia) of the Western rivers is a representative of 



i The observations of Scott and Osborn should not be overlooked, though pub- 

 lished in England. 



