AND ZYGOTES I\ MOSQUITOS INFECTED WITH MALARIA. 5 



(e.) If the normal structures of the stomach arc known there is no difficulty in 

 recognising zygotes.* (Fig- -!•) 



'n W..fili 



'"» « »d Cn< fe/^ 



Fig. 4. — Microscopic appearance of mid-gut, showing cell-structure and zygotes. 



(1.) The younger forms are clear oval or round bodies 6-7/.(, i.e., about the size 

 of a red corpuscle, containing definitely seen -pigment granules. 



(2.) The larger forms have a distinct cyst ivall {oocysts) and still retain pigment 

 which is unmistakable. 



(3) The largest oocysts have lost their pigment and are clearly defined cysts 

 (40-60/x) filled with hundreds of sickle-shaped bodies (sporozoits) which escape on 

 rupture. 



(/.) " Black spores " (Ross). — Although very many dissections of Anophelines 

 were made by Christophers and myself in Africa, these brownish or black 

 sausage-like bodies which sometimes are found in the large oocysts were never 

 seen by us. In India we saw them only twice, in hundreds of dissections, and on 

 both these occasions they were in the region of the salivary gland. They are, 

 however, far commoner in the oocysts of Culicines fed on Pruteusoma. According 

 to some authors they are parasitic sporozoa, but nothing is known as to their 

 life-history. 



Staining of Zygotes. 



(a.) Draw some 10 per cent, formalin solution luider the cover-glass by means 

 of blotting paper, and float ofif the cover-glass carefully. The stomach will 

 probably remain attached to it. 



{h.) Wash in water. 



(c.) Stain lightly with methylene blue. 



{d.) Wash in water, dehydrate, clear in xylol. 



(e.) Mount in balsam. 



Good preparations are easily obtained in this way. 



* Zygotes if scanty (1 or 2) will be found at the bottom end of the stomach nearest the 

 Malpighian tubes. 



