86 University of California Publications in Zoology [Vol. 18 



spore, small zooid forms, the nectomonads or free flagellated forms 

 and the haptomonads or attached forms. The infection of this division 

 of the digestive tract is much greater than of any other part. It is 

 in this part that the infection is retained after the first infection. 

 The oval spore forms and zooids are readily found in nearly all the 

 preparations of this division of the mid-gut. There is no evidence 

 thus far to indicate that either the spore forms or the zooids develop 

 into flagellates. 



Nectomonads (figs. 23-26) are found in large numbers in the 

 pyloric expansion. Binary fission forras (fig. 24) are found fre- 

 quently and this probably accounts for the reduced size of such free 

 forms as figures 23 or 24, and the production of the long, slender 

 haptomonads which will be described shortly. Figure 23 shows a 

 different type of nucleus which can not be regarded as being char- 

 acteristic of the free nectomonads. It is doubtless a sign of degenera- 

 tion but in these parasites it is not the most prevalent indication of 

 degeneration. The preparations frequently show nectomonads with 

 a sticky periplast. As a result of this the individuals adhere to each 

 other and collect many bacteria on the body surface. Many others 

 show the vacuolated cyotplasm or one stage farther wherein the 

 cytoplasm has completely degenerated leaving only the nucleus, para- 

 basal body, the rhizoplasts and the flagellum still attached to each 

 other 



Haptomonads are of two general types in the pyloric expansion. 

 In the upper or anterior part there are found the attached, elongate, 

 slender forms (fig. 23) like those which occur in the posterior portion 

 of the mid-stomach. Gradually gradating from these long forms to 

 the small pear-shaped forms (figs. 20-22) are the intermediate forms. 

 No evidence has been found to show that the haptomonad forms 

 become detached and encyst to form the oval spores. On the 

 contrary the cytoplasm of the haptomonad forms like that of the 

 nectomonad forms is vacuolate and degenerative in structure. Fur- 

 thermore there is no evidence that any of these nectomonads or 

 haptomonads normally succeed in reaching the rectum through the 

 intestine of Euryophthalmus convivus. 



Of the three forms which migrate into the pjdoric expanse the 

 oval spore forms are probably the true infective agents while the 

 nectomonads and the haptomonads are forms in degeneration. 



