534 JOSEPH STAFFORD, 



reservoir at the meeting of the transverse canals, when everything 

 goes to show the unimpeded supply of yolk waiting to be made use 

 of, it is utterly incomprehensible that the minimal quantity of yolk 

 contained in this organ should be that required for the making of 

 eggs. It is very unlikely that a material of such constant use should 

 have to travel against the outflow of primitive ova, away through a 

 narrow canal to the posterior end of the animal, and again be with- 

 drawn under still more unfavorable conditions. Besides, we have no 

 proof that yolk, when once in this organ, ever comes out again. The 

 conditions are against the supposition, for the pressure from distention 

 of the anterior ducts is in the opposite direction; in muscular con- 

 tractions the pressure from the crowding together of more or less 

 voluminous organs would be from the middle of the animal backwards; 

 situated as it is, behind the great mass of genital and intestinal or- 

 gans in the loose parenchyma, with nothing near it but the excretory 

 vessels and a few folds of the uterus, nothing but the possession of 

 a strong musculature of its own could again expel its contents. More- 

 over, the place of use of the yolk is in the opposite direction from 

 the mouth of the unpaired yolk gland. The yolk in this organ soon 

 becomes brownish, its cells disintegrated letting the globules free, 

 and altogether it shows signs of abnormal changes. Most important 

 of all is that this organ has essentially the same position as an organ 

 of pretty constant occurrence in the Trematode group. At its proxi- 

 mal end this canal has the same relations to the rest of the genitalia 

 as the Laurer's canal of the great majority of well known Trematodes. 

 The Laurer's canal of other Trematodes shows so much variation in 

 its peripheral opening that we need not be surprised to find, here, 

 in this otherwise erratic worm, an especially peculiar modification of 

 an organ, which, though not of primary importance to the individual, 

 and perhaps becoming rudimentary, may yet play some role in the 

 economy of the organism. The structure aud contents of the three 

 stages I have described seem to me only explainable upon the sup- 

 position that the protoplasmic parts of the cells that make their way 

 into this organ become absorbed into its walls, and the parenchyma 

 cells immediately surrounding it, while some of the insoluble nuclear 

 contents remain behind. The cells of its walls, in the presence of 

 this additional food supply, are excited to more vigorous growth, 

 some of them retain their power of division, and by their increase in 

 number, and their albuminous contents, they come to form a mass 



