460 E. A. MINCHIN ON SOME DETAILS IN THE ANATOMY OF 



perhaps specimens cleared in potash, would he necessary to 

 determine this point. 



The spermatozoa live a very long time, as is well known, in 

 the receptaculum, and are used up gradually to fertilise the eggs 

 as they are laid. In the queen-bee it is known that the insect 

 lays fertile eggs for at least three years, and in some other 

 insects this length of time may be exceeded by a considerable 

 amount. The muscles seen in connection with the receptaculum 

 and its duct may be connected with the function of passing out 

 the spermatozoa. A contraction of the muscle connecting the 

 horn-shaped chamber of the receptaculum with the main chamber 

 would probably force some spermatozoa out into the duct. On 

 the other hand, a contraction of the " bowstring " muscle of the 

 terminal organ would bend the " bow," and so occlude the duct, 

 preventing anything from passing out. There does not seem to 

 be any apparatus for forcing the spermatozoa up the duct and 

 into the receptaculum, but this is effected probably during 

 copulation by the male intromittent organ possibly by the 

 problematic " corkscrew-organ." The spermatozoa in the recep- 

 taculum must be kept alive a long time, and may be nourished 

 by the secretion of the glandular cushion round the origin of 

 the duct, while the rounded gland-cells on the duct may perform 

 some similar function for the spermatozoa during their passage 

 down the labyrinthine duct, the great length of which is difficult 

 to explain in a plausible manner. All these suggestions have, 

 however, only the value of more or less probable surmises. 



In the tsetse-fly the receptaculum is a paired organ, and in 

 the gnat there are three receptacula, one median and two 

 paired. In that of the flea there is no sign of any double 

 structure. 



V. Muscle-cells of Stellate Form in the Oesophagus of the Flea. 



In some of our smear-preparations of teased flea -stomachs, 

 made in the course of our investigation into the development of 

 Trypanosoma lewisi, there were to be found occasionally specimens 

 of the flea's oesophagus, which adhered to the cover-glass after it 

 had been fixed with Maier's sublimate-alcohol mixture and 

 stained by Heidenhain's iron-haematoxylin method. In such 

 preparations it is easily seen that the oesophagus has a beautiful 



