346 KOFOID AND SWEZY. 



pentis (Dobell) with the expectation that later work will clear up the 

 differences between, or the identity of the species of EutricJwmastix 

 in lizards and snakes. 



The Trophozoite. 



This small flagellate has an elongated or a stout body of variable 

 outline, ovate, obovate, pyriform, slightly asymmetrical or more or 

 less irregular, the latter feature resulting doubtless from its amoeboid 

 activities on the slide as substrate. Free-swimming forms tend to be 

 elongated and individuals resulting from recent division are typically 

 elongated (PI. 7, Fig. 79). The stouter forms predominate in intestinal 

 smears. The mucus of the intestinal wall and its glands appears to be 

 the medium in which the less active and larger stages prior to binary 

 and multiple fission are developed. The range in form in our material 

 from long slender to short stout (PI. 7, Figs. 79, 81) ones is analogous 

 to that noted above in Trichomonas aujusta. It may also in this form 

 represent to some extent a cyclic change from the slender type result- 

 ing from binary or multiple fission to the stout form preceding one or 

 both of these forms of reproduction. It is possible that copulation 

 may precede both or either of these forms of multiplication, especially 

 the latter, but no evidence of it has been detected in the course of our 

 examination of the material. Individuals in the metaphase of mitosis 

 (PI. 7, Fig. 84) and in multiple fission (PI. 8, Fig. 99) become more or 

 less spheroidal or ellipsoidal. 



Since the whole range in form occurs in a single host (Crotalus) 

 and since we can find no group of morphological characters to dis- 

 tinguish species within this complex we regard all of the forms as in 

 the cycle of one species. The range is sufficiently wide to include the 

 slender form figured by Blochmann (1SS3) as Trkhomastix lacertae 

 Biitschli from Larerta agllis, the stouter one figured later by Prowazek 

 (1904) from smears from the intestine of Lacerta muralis, and the stout 

 forms figured by Dobell (1907) as Trichomastix serpentis from the 

 rectal contents of Boa constrictor. Dobell states that his culture con- 

 tained many involution forms. 



The length from anterior end to the posterior tip of the axostyle 

 in our material ranges from 8-20 fj. and is usually 13-15 jjl in active 

 vegetative forms. The diameter varies greatly in different individuals, 

 even of the same length and even in the same individual under differ- 

 ent conditions of amoeboid activity. It ranges 4 /x in very slender 



