438 The Ohio Naturalist. [Vol. VI, No. 3, 



spermatozoa surround a mass of protoplasm, within which their 

 heads are buried. This mass, greatly vacuolated, and clearly 

 in process of degeneration, represents the granular mass fonned 

 by the central ends of the spermatids. Thus only a slight por- 

 tion of the original cytoplasm takes part in the formation of the 

 spermatozoan, by far the larger portion being cast aside. It is, 

 of course, possible that this mass may serve for a time to nourish 

 the spermatozoa, although it would seem likely that the blood 

 lymph contained in the coelom would suffice to perform that 

 function. 



In the maturation of the male germ cells one point is espe- 

 cially noteworthy, namely, the appearance of a large nucleolus 

 in the spermatocytes of both orders and in the spermatids. 

 With but rare exceptions, throughout the animal kingdom the 

 maturation divisions occur without the intervention of even a 

 brief resting stage. The formation of a nucleolus, then, of such a 

 considerable size in comparison with the cell size is remarkable 

 in indicating the occurrence of a long resting stage between the 

 two maturation divisions, and also a long pause before the 

 metamorphosis of the spermatid into the spermatozoon. 



With respect to the sexual reproduction of Aelosoma several 

 questions arise, which are still unanswered. For example, it is 

 important to discover what factors determine the occurrence of 

 sexual reproduction; whether due to changes in temperature, 

 food supply, or to some other cause ; the breeding habits should be 

 carefully studied, and the complete history of the sex cells 

 recorded. Species of Aelosoma are found abundantly in our 

 inland ponds and streams, and are ea-ily kept in aquaria 

 throughout the year, I hope these facts may stimulate some 

 one to the further investigation of the life history of this beautiful 

 form. 



A PRELIMINARY REPORT ON THE MOSQUITOES OF OHIO.* 



A. F. Burgess. 



Since it was positively demonstrated that mosquitoes are the 

 means of communicating yellow fever and malaria, many 

 investigators have given attention to collecting, studying and 

 describing these insects; hence, during the past five years rapid 

 strides have been made in our knowledge concerning this 

 interesting family. 



In the catalog of North American Diptera, published by 

 Mr. J. M. Aldrich, in 1905, thirty genera, containing one hun- 

 dred and sixty-five species of Culicidae, are listed. Some of 

 these species are tropical or sub-tropical forms which do not 

 occur in northern latitudes. 



* Read at the meeting of the Ohio St. Acad, of Sci., Cincinnati, Dec. 2, 1005. 



