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DIMORPHISIVI IN THE SPERMATOZOA OF THE FLEA 



AND BLOW-FLY. 



By T. a. O'Donohoe, I.S.O. 



{Bead June 27th, 1911.) 



Plate 11. 



If the testis of a flea {Pidex hominis) be placed in a drop of 

 water on a clean slide and punctured with a fine needle, under a 

 low power, fine hair-like organisms will be seen to burst forth, 

 and by gently moving the testis these are easily spread about on 

 the slide, so that when the drop of water is allowed to dry up 

 these minute organisms can be stained in dilute carbol-fuchsine 

 or gentian violet, and mounted in Canada balsam for examination. 



A slide thus prepared was hurriedly shown by me some weeks 

 ago at one of our Gossip Meetings. This I did before carefully 

 examining the preparation myself, so that on looking at it more 

 carefully on the following day I was much surprised to find that 

 these spermatozoa differed very much both as to form and size, 

 that in fact there were two distinct kinds. At that time I was 

 not aware that any animal was endowed with more than one kind 

 of spermatozoon, and some of my friends suggested that the two 

 forms which I had discovered in one flea were nothing more than 

 developments of one form. 



This seemed to me at that time a reasonable objection; but 

 finding that a flea caught in the act of copulation yielded the 

 same two forms, this objection became untenable inasmuch as 

 the spermatozoa would, in my opinion, be fully matured in such 

 a flea. With a view to learning whether cases of dimorphism in 

 the spermatozoa of animals were recorded I had recourse to 

 several volumes of the Journ. R. M. S., in which I found extracts 

 from various writers showing that in some animals two forms of 



