H ARC ITT. 



[VOL. I. 



regenerate or coalesce. 



III. Grafting. 



Hydroids. - - The work upon Hydroids was restricted chiefly 

 to species of Eudendrium, Pennaria, and Parypha, though a 

 few experiments were tried upon Campanularians. Upon the 

 latter the results were almost entirely negative, though for this 

 no apparent cause was ascertained. The experiments were 

 not of sufficient numbers, nor of sufficiently varied conditions, 

 to warrant any conclusions as to the incapacity of these to 



Time was not adequate to extend the 

 attention to this group which might 

 have resulted more favorably. Again, 

 the relatively small size of the members 

 of this group available was a further 

 embarrassment to successful experimen- 

 tation. However, neither of these is 

 offered as sufficient account of the neg- 

 ative character of the experiments. In- 

 deed, the work of Davenport ('94) on 

 Obelia is strongly affirmative, at least 

 so far as regeneration is concerned. 



Experiments upon species of the 

 genera named were specially successful. 

 While of course in all such work a large 

 number of failures must result, yet when 

 the difficulties of manipulation and the 

 artificial conditions necessary are considered, this is not strange. 

 While no mathematical estimates were made as to the ratio 

 of successful experiments, I think it may be safely said that 

 at least 20 per cent of all were successful. It need hardly be 

 pointed out that results varied materially in both the time 

 necessary, and the degree of perfection, in the coalescences. 

 This will be noted in detail in connection with the several 

 experiments described. 



A comparison of the several figures will perhaps indicate in 



general better than words the methods and results. Cf. Figs. 1-6. 



The union between sections of the same species was usually 



quite perfect within from eighteen to thirty-six hours. A 



FIG. 3. 



