1914] A New Cestode from Amia Calva L. 107 



The oviduct begins on the ventral surface of the ovarian isthmus 

 with the o o c a p t which is a broad funnel-shaped or hemispherical 

 structure directed ventrally in the median line (Fig. 27). The diameter 

 of the latter, using the outer limits of the circular musculature as the 

 boundary, since the organ is very gradually continuous with the wall of 

 the isthmus, varies from 15 to 25/i. It is lined with a cuticle-like sub- 

 stance, which shows no nuclei for a short distance, and is surrounded by 

 a system of circular muscles, arranged and extended quite like those of 

 the spermaduct and posterior end of the receptaculum seminis. Further- 

 more, the resemblance in structure is the more exact from the fact that 

 the constricted portion of the duct, which immediately follows the 

 muscular funnel, is surrounded by radially arranged nuclei, many of 

 which belong, of course, to the myoblasts of the circular fibers. The 

 constricted part has a diameter of from 8 to g/j.', after which the oviduct 

 gradually enlarges to i^jj., as it courses to the right or left and posteriorly 

 until it meets the spermaduct almost in the median line of the proglottis. 

 The wall is made up of a ciliated epithelium, in which are to be seen one 

 layer of nuclei but no distinct cell-boundaries in the somewhat vacuolated 

 cytoplasm, supported by a well-developed basement-membrane. 



A short distance from its union with the spermaduct the oviduct is 

 joined by the short duct from the yolk-reservoir. Just behind this point 

 there is a slight constriction, around which the circular muscles are 

 augmented in number to form a small sphincter while they are accom- 

 panied by a few longitudinal fibers. 



Two vitelline ducts, each about 6ij. in diameter, collect yolk 

 from the lateral fields of vitelline follicles and pass towards the median 

 line to unite either within or outside of the generative space ventral to 

 the ovary. Union within the latter is the usual arrangement, in which 

 case each duct is accommodated in the groove situated on the ventral 

 surface of the ovary between the oocapt and the anterior end of the limb 

 on each side. Each of these ducts may receive material from a few 

 follicles on the opposite side of the proglottis, but, in general, it collects 

 from the same side to which it is directed. Their walls are composed of 

 a thin epithelium, showing small flattened nuclei distributed at wide 

 intervals, on the whole resembling those of the vasa efferentia. Their 

 courses are easily followed by observing the, in many places, greatly 

 extended yolk-cells on their way to the yolk-reservoir (Fig. 29b.). On 

 the other hand, the arrangement and structure of the smallest ducts in 

 immediate connection with the yolk-follicles were not determined to the 

 writer's satisfaction, since the latter are packed so closely together; but 

 from various appearances they seem to anastomose. 



