102 University of California Publications in Zoology [Vol. 20 



anterior end drawn out into a short cone-shaped projection. This 

 is terminated by a small, transparent, caplike structure, the oper- 

 culum (fig. A, oper.), which covers a cup-shaped depression (pi. 13, 

 fig. 10). This is similar to the structure of the anterior end of 

 Trichonympha campanula. No evidences have been found which 

 would indicate the function of this peculiar formation. It is the 

 only part of the surface of the body bearing any resemblance to a 

 cytostomal opening into the endoplasm, j'et we have no evidence that 

 it is used for that purpose. 



The surface of the anterior and sometimes even of the middle 

 portions of the body is marked by longitudinal ridges which extend 

 from the operculum posteriorly (fig. A, surf. rdg.). In the posterior 

 regions these are entirely lacking, the surface having a smooth, 

 unbroken outline. 



Nettromotor System 



The neuromotor system of Leidyopsis resembles that of TricJio- 

 nympha.. It consists of a highly developed, anteriorly located 

 centroblepharoplast, numerous flagella, and two sets of fibers, the 

 oblique fibers in the ectoplasm and the longitudinal myonemes in the 

 endoplasm. The transverse myonemes of Trichonympha are not 

 found in this form and the othere are not so well developed as are 

 those of that genus. 



BcTOPLASMic Structures 

 The division of the body into ectoplasm and endoplasm is clearly 

 marked only in a narrow zone surrounding the cone-shaped anterior 

 end of the body. Here it presents the three distinct layers so striking 

 in the ectoplasm of Trichonympha, but these soon fade out, though 

 the myonemes and surface ridges can be traced farther posteriorly, 

 the latter usually having a length of one-third to one-half that of 

 the body. Anteriorly the ectoplasm is thick around the base of the 

 cone, becoming thin posteriorly until it merges into the thin periplast 

 of the middle and posterior regions of the body (fig. A). It is com- 

 posed of an outer layer of surface ridges ( fig. A, surf, rdg.), an 

 alveolar layer (alv. l), and a narrow, inner ectoplasmic layer. These 

 are traversed by the oblique fibers and also contain the basal granules 

 of the flagella. These separate structures will now be discussed in 

 detail. 



