PROCESS OF EGG-MAKIXG IN A TREMATODE. 23 



certain, from what could be made out from the mechanism of the 

 Hving worm, that one result of the rush of yolk in passing the 

 germarium (see arrow in Fig. 3 lying partly on the yolk reser- 

 voir), was to draw a germ-cell from the duct (c) (see arrow on 

 •germarium, Fig. 3), no cell was seen to leave its place in the 

 germarium to enter the common duct (tv/). The reason for this 

 failure to see a germ-cell join the mass of yolk appeared when 

 sections were studied. It was then seen (Fig. 5) that the germ- 

 duct (f) leaves the germarium on its dorsal side, and is there- 

 fore seen only in end view when the worm is flattened out on the 

 slide. In so much of the duct as was visible there were many 

 free germ-cells, all of them oscillating more or less and thrown 

 into vigorous agitation at the time when a mass of yolk was 



Fig. 5. Transverse section showing junction of ducts from yolk reservoir and 

 •germarium in common duct. Actual thickness of body through germarium 0.5 mm. 



passing the germarium. If a cell were to leave the germarium 

 its motion would be in a direction perpendicular to the eye, and 

 therefore could not be detected. The portion of the duct which 

 proceeds cephalad is somewhat concealed by the germarium. 

 Hence here is one point in the process of egg-making, which, 

 although perfectly obvious from the construction of the mecha- 

 nism, was not actually seen. As the duct is at first perpendicular 

 to the surface of the worm, it is obvious that the progressive 

 motion of the germ-cell cannot be detected whether viewed from 

 the dorsal or the ventral side. 



The mass of coarsely granular yolk (Fig. 3, r) passes without 

 pause and with comparative rapidity along the common duct (cd) 

 to the ootype {em), which is simply a specialized part of the com- 

 mon duct. As soon as the mass of yolk reaches the ootype the 

 passage closes by the approximation of the walls of the duct 



