HARGITT. 



[VOL. I. 



FIG. 5. 



elusions. Of Pennaria, only one species was available, and 

 the same was true of Parypha. Of the species of Eudendrium 

 there have been several indicated, but their distinct- 

 ness is to my mind open to serious doubt. 



If the distinctness of Agassiz's species of E. dispar 

 and ramosnni is to be maintained, then the grafting 

 of these has been as clearly established as that of 

 the different sexes. It would not be strange should 

 closely allied, though definitely distinct, species be 

 found to coalesce in these organisms, for such has 

 been long known among plants, and shown for 

 animals by the recent experiments of Born ('96), 

 Crampton ('97), Harrison ('98), and others. But so 

 far as I am aware it has not hitherto been demon- 

 strated for the Hydroids ; indeed, most of such 

 efforts have been negative in results. 



As to the coalescence between specimens of 

 different genera, the experiments seem to be conclusive and 

 wholly negative. Out of a considerable series, while there were 

 indications of temporary union, in no case did it become con- 

 clusively permanent. The most favor- 

 able indications were upon Eudendrium 

 and Pennaria, Hydroids of very similar 

 size, structure, and habit ; but after 

 repeated experiments under different 

 conditions the results were as already 

 indicated. In Fig. 6 it will be noted 

 that the usual secretion of perisarc at 

 the points of contact has been de- 

 posited, and apparently by the coopera- 

 tion of both sections ; still at no time 

 were there evidences of organic union 

 of the coenosarc, and later this was 

 distinctly withdrawn, and the sections 

 continued an independent existence, 



FIG. 6. 



each producing new hydranths, though 



in the case of Eudendrium they continued rudimentary in 

 the specimen figured. 



