THE GREEN CELLS OP CONVOLUTA EOSOOFFENSIS. 177 



infected Convoluta escape from the body, live freely again, 

 and again infect a young animal ? and what is the origin of 

 the cells which in the preceding experiments developed on 

 the capsule and subsequently infected the larval Couvolutas ? 

 are they derived from the interior of the body of the egg- 

 laying parent or from the environment? 



With respect to the first question, we have failed, as 

 Haberlandt failed before us, to cultivate in nutrient media 

 green cells liberated from the body of the adult. But more 

 convincing than these negative results are those set forth in 

 Table I (Column A) and Table III (column headed " Filtered 

 sea-water with adults^'). In these places are recorded the 

 results of experiments in rearing young animals in association 

 with large numbers of adults which had been washed many 

 times in filtered water. Under these circumstances the larvae, 

 though surronnded by great numbers of adults, many of 

 which, having ruptured in the course of egg-layiug, had dis- 

 charged large numbers of green cells, failed for twenty days 

 to show sign of infection. It thus appears certain that the 

 ordinary green cells, as they exist in the body of one animal, 

 are incapable on their discharge from that animal of infecting 

 anotlier. Indeed, under no conditions known to us do the 

 green cells of a Convoluta ever escape alive from the bod3^ 

 Each Convoluta leaves the body of the mother as a colourless, 

 uninfected animal; as such it hatches out from its capsule, 

 and the cells which then infect it are derived from the 

 environment, neither they nor their direct ancestors ever 

 having been before within the body of a Convoluta. We 

 return to this matter again in Section V, where we give an 

 account of the histological changes which the green cells 

 undergo in the course of their development in the body of 

 Convoluta, and show that these changes account for the at 

 first sight extraordinary facts just described. 



There remains to be considered the second question — as to 

 the origin of the green cells which make their appearance on 

 the capsules and which served in various of the foregoing- 

 experiments as sources of infection to larval Convolutas. 



