1917] McCulloch: Crithidia euryophthalmi 83 



Forms from the Crop 



Oval Spore Forms. — In the crop of approximately twenty per 

 cent of the nj^mphs and two per cent of the adults oval spore forms 

 together with the developing forms can be found. The oval spore 

 forms have been regarded as the infective spore taken up casually 

 with the food by the host. They are 3.2/^ long and lAfj, wide (fig. 2). 

 The anterior end is slightly pointed while the posterior is blunt. They 

 have a very characteristic shape and retain the haematoxylin stain 

 for a longer period than the other forms of the flagellate. Internally 

 the nucleus and parabasal body are relatively large. These two 

 deeply staining structures are connected by the nuclear rhizoplast 

 which retains enough of the stain to make it readily visible under 

 a high-power binocular microscope. The oval spore forms with their 

 characteristic staining capacity, size, and nuclear structure can be 

 pointed out among the parasites of the mid-stomach (fis. 1, 19) and 

 of the pyloric expansion (fig. 27). The development of these oval 

 spore forms into flagellates has been followed in part in the living 

 material. The several stages in development have not been followed 

 for the same individual, the process having been studied in a dis- 

 connected manner. 



Developing Crithidial Stages. — The oval spore form begins to 

 unfold slightly at the anterior end. The flagellum is bent back along 

 the body as far as the parabasal body. This straightens out anteriorly 

 and accompanjnng this change there is an elongation of the posterior 

 end (fig. 3). The whole series of developing forms gradating from 

 the non-flagellated forms (fig. 2) to the large elongated flagellates 

 can be found readily in almost all preparations of the infected crops. 



Multiple Fission — Somatella 



In four instances out of two hundred crops examined, spherical 

 forms were found showing a variable number of nuclei and parabasal 

 bodies together with a multiplication of the number of flagella. The 

 flagella may project from spherical surface in various directions. 

 The origin of the several nuclei and parabasal bodies within this 

 plasmodial mas has not been followed in detail; at the present time 

 these spherical forms are regarded as somatellae which are common 

 to many of the flagellates. There is little evidence to show that this 

 process of multiple fission is of any importance in the multiplicative 

 phase of the parasite, since it occurs so rarely. Its relation to a 



