448 Dr. C. W. Daniels. On Transmission of 



This appearance I frequently observed in the other series of infected 

 insects already mentioned. 



These threads, Boss's germinal threads, are sickle-shaped bodies, about 

 14 or 15 fj. in length. They stain with logwood or methyl blue, but 

 not strongly. On adding water or Farrant's solution they lose their 

 shrivelled appearance,"and become more rounded. Nearer one end than 

 the other is an unstained portion (1 nucleus). They show no signs of 

 movement ; but as they are invisible in water, and only become visible 

 when shrivelled by the salt or stained, it may be doubted if they have 

 been seen alive. 



If the thorax of the mosquito at a somewhat more advanced stage in 

 the development of the proteosomal coccidium is incised, similar threads 

 will be found in the fluid exuded, if salt solution is added. In this case 

 ruptured cysts can be found in the stomach wall. 



The relation of the infection to the veneno-salivary gland involves 

 a difficulty not met with in any other part of the examination. 



The dissection of the stomach is easy ; that of the salivary gland in 

 its entirety is not, and for some reason appears to be more difficult in 

 the old infected mosquitoes. Any rough manipulation results in the 

 detachment of the cells, and little more than the duct is left. In most 

 cases, however, even in old infected mosquitoes, one entire gland, or 

 portions of both, can be exposed in fair condition. 



In every case where this was done, and in which germinal threads 

 were found in the body-fluids, the germinal threads were also found 

 in some of the cells of the salivary gland. I failed to find similar 

 threads in the large number of salivary glands obtained from unin- 

 fected mosquitoes bred from larvae, or caught about the laboratory, or 

 from mosquitoes at the earlier stages of proteosomal infection. 



The affected cells, as they have a granular appearance, can be dis- 

 tinguished with a low power ; the unaffected cells are quite clear. 



With a high power, if not very numerous, the isolated germinal 

 threads can be clearly distinguished in the cells ; they are recognised 

 by their peculiar shape and shrivelled appearance (the examination 

 must be made in salt solution). If numerous, the individual threads 

 can be better made out in the cells of the salivary gland than in the 

 coccidia of the stomach wall ; but, as in the case of the latter, pressure 

 on the cover glass will rupture the cell, and the germinal threads are 

 then poured out. 



The threads do not fill the cell. There is a faintly granular cres- 

 centic portion on the side most remote from the duct which, in many 

 cases at least, is free from threads. The part of the cell in which the 

 threads lie must be nearly fluid, as it permits oscillation of the threads 

 to take place. 



The whole of the veneno-salivary gland is never involved. In one 

 dissection made by Ross the cells in both middle lobes and in no other 



