IMPLANTATION OF THE GLOCHIDIUM ON THE FISH 7 



of parasitism and the temperature of the water has not been 

 quite so definite. In Symphynota complanata, with a hooked 

 glochidium, the time has varied from 9 to 15 days at tempera- 

 tures varying from 16-18 C, while in Lampsilis ligamentina, 

 which has a hookless glochidium, the period has been somewhat 

 longer at these temperatures, namely, 14 to 36 days. In the 

 latter species, the rule that the parasitism is shorter, the 

 warmer the water, is not uniformly applicable, for I have ob- 

 served certain cases in which this relation did not hold. For 

 example, I have recorded a period of 14 21 days at an average 

 temperature of 16.4 C, while in other experiments at 19 or 20 

 C it has taken from 19 to 36 days for the development to be com- 

 pleted. In the latter case, although the temperature was three 

 or four degrees higher, the period was considerably longer 

 instead of being shorter as might have been expected. 



In those infections which lasted from 9 to 36 days the 

 young mussels were set free during a period of 4 or 5 days. 

 This agrees very well with Harrys' results, since he finds that 

 the duration of the period of liberation is 5 6 days and that 

 more mussels drop off during the middle days of this period 

 than the first and last. 



IMPLANTATION OF THE GLOCHIDIA 



Sections of glochidia attached to the gills and fins, cut 5 jj. 

 thick, and whole mounts of glochidia on gill-filaments and on 

 fins were studied. The living larvae, also, at various times 

 after their attachment to the gills and fins were carefully 

 examined. 



At once upon attachment of the glochidium to the fish, the 

 epithelium of the latter in the immediate neighborhood of the 

 glochidium begins a rapid proliferation. Faussek (4) and 

 Harms (8) believe that this proliferation of the epithelial cells is 

 caused by the irritation produced by the wound, and that it 

 is to be regarded merely as a healing process. At all events the 

 glochidium exerts a stimulus upon the cells of the host which 

 are thrown in consequence into active division. The cells divide 



