THE HJIMOFLAGELLATES. 169 



during the next digestive period. Hence if a gnat becomes successfully 

 infected, it remains so throughout life. 



The other parasite described by Schaudinn, Trypanosoma ziemanni, 

 differs slightly in its behaviour in the gnat. Towards the end of the first 

 digestive period the active parasites, instead of collecting in the anterior 

 part of the stomach, press backwards and enter the Malphigian tubules, 

 where, after undergoing multiplication, they come into relation with the 

 excretory epithelium and assume a resting-phase. When the next supply of 

 food has entered the stomach, the Trypanosomes again become active, and, 

 after the process of epithelial regeneration, are carried along with masses of 

 disintegrated cells into the colon, where the subsequent course of events 

 agrees with that just related. The author adds that he has only twice 

 found this form in the salivary glands, and does not think this is a normal 

 habitat of the parasites. 



Befoi'e leaving the consideration of the Trypanosomes in 

 their relation to the Insect, a very interesting discovery of 

 Schaudinn's must be mentioned, namely, the occurrence of 

 true hereditary infection. Both the parasites described (and 

 also, indeed, the commensal Fungus) inay be inherited by the 

 gnats. After breaking through the wall of the colon some of 

 the Trypanosomes, instead of being carried forwards, may 

 pass to the ovarian follicles, there penetrate into the eggs of 

 the youngest, and so infect a succeeding generation. As a 

 rule only few parasites, mostly females, thus penetrate into 

 the ova ; once there they assume a gregariniform resting- 

 conditiou, in which they remain throughout the development 

 of the embryo. When at length the imago first sucks blood 

 these female forms undergo parthenogenesis, and the body of 

 the guat becomes overrun with Trypanosomes. Sometimes, 

 however (in cases of ample nutrition), the parasites multiply 

 in the yolk of the growing eggs, and may become so numerous 

 that castration results. 



Schaudinn has also ascertained that a similar hereditary infection of 

 Anopheles with the tertian parasite occurs. Thus true hereditary infec • 

 tion in the Sporozoa is by no means limited to the case of Glugea 

 bombycis, and it is highly probable that the infection of the progeny of 

 ticks (Rhipicephalus = Boophilus) by Piroplasma also belongs in 

 this category, although the parasites have not yet been demonstrated 

 actually in the ova of the mother-individual, 



