128 University of California Publications in Zoology [Vol. 16 



The flagellate from insects has come to be generally accepted as the 

 type species of the genus, with the name Monocercomonas melolonthae. 

 This is a flagellate about 12 to 15 /x long and 8 to 11 /x wide, ovoidal in 

 outline, with the broader end anterior, and more or less pointed at the 

 posterior end (pi. 16, fig. 3). Forms are occasionally met with which 

 are spheroidal in outline. The four equal flagella extend anteriorly, 

 arising at the anterior extremity of the body, usually in two groups of 

 two flagella each from two blepharoplasts sometimes more or less 

 widely separated from each other. Arising from one blepharoplast is 

 a slender, usually darkly-staining axostyle which curves around the 

 nucleus and passes backward to the posterior end of the body. This 

 differs from the axostyle in Trichomonas (Kofoid and Swezy, 1915, 

 a, b) and Hexamitus (Swezy, 1915a) as well as that in Giardia (Kofoid 

 and Christiansen, 1915) in that it seems to occupy a position along the 

 surface of the body and not in the center of the protoplasm. It does 

 not project beyond the body but terminates in the periplast at the 

 posterior extremity (pi. 16, fig. 1). Its position, relations, and struc- 

 ture would strongly sugge.st the correctness of the interpretation which 

 has been placed upon the axostyle in Trichomonas by Kofoid and 

 Swezy (1915&) namely, that it is an intraeytoplasmic flagellum, which 

 in Monocercomonas has not yet migrated to the deeper portions of the 

 cytoplasm. 



The large vesicular nucleus is situated in the anterior part of the 

 cell, immediately behind the blepharoplasts which rest upon the 

 nuclear membrane. The chromatin is massed in a large karyosome 

 centrally placed, often with smaller granules occupying a position 

 against the nuclear membrane (pi. 16, fig. 2). The nuclear membrane 

 itself often takes a dark stain with iron haematoxylin. 



There is neither cytostome, undulating membrane, nor trailing 

 flagellum present. 



A flagellate has been figured by MacKinnon (1912) from the larva 

 of the erane-fiy Tipula, which she considers identical with the species 

 described by Grassi as M. melolonthae. Jollos (1911) describes a 

 flagellate from the larva of Cetonia which he places in the genus 

 Monocercomonas as M. cetoniae Jollos. 



Franca (1913), also working on insect lai'vae, figures an organism 

 from the larvae of Phyllognatus and Oryctes which shows the generic 

 characters of Monocercomonas and evidently belongs to that genus, 

 probably to the species mdolonthac. 



