43 ^ 
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 formed 
by the central ends of the s])ermatids. 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 sj^ermatozoon. 
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 re])roduction ; 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 easily 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 190.5, 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. .\cad. of Sei., Cincinnati. Dec. 2. 190.5. 
