THE MIGRATION OF REPRODUCTIVE ORGANS 

 FROM PARENT TO BUDS IN HYDRA. 



GEORGE W. TANNREUTHER, 



ZOOLOGICAL LABORATORY, UNIVERSITY OF MISSOURI. 



The germ cells of hydra, as far as we are able to interpret by 

 means of a microscopic study of carefully prepared sections, 

 originate directly from the ordinary interstitial cells. It is 

 true, however, that some investigators advocate the specificity 

 of the germ cells. But the species studied gave no evidence of a 

 specific line of germ cells. It is not my intention to take up a 

 careful study of the germ cells in hydra, as to their method of 

 origin and history, but rather to consider them from the stand- 

 point of their place of origin. That is, do the reproductive 

 organs originate directly on the forming buds, or are they formed 

 on the parent hydra and later migrate to the buds during their 

 development. 



Investigators have reported the presence of sex organs on the 

 buds in hydra, but in no case has it been definitely stated that 

 these organs originated directly from the ectoderm of the young 

 buds on which they were found. 



Fig. i represents a camera drawing of Hydra vulgaris in a par- 

 tially contracted condition, with five buds in different stages of 

 development, and thirteen spermaries. Most of the spermaries 

 were completely formed before budding begun. In no instance 

 did the spermaries originate directly on the buds, but migrated 

 with the cells of the parent to those of the forming buds. 



Diagram A, I, represents a small portion of the parent hydra 

 extended, with a bud in its initial stage of development. 

 The area between R-G on either side of the bud, indicates 

 the region of growth or the region that contributes directly to 

 the formation of the bud. Reproductive organs found within 

 this region (R-G), migrate from the parent hydra to the bud. 

 Those outside of this region of growth never reach the bud, but 

 in most instances retain their original position, while the buds 



418 



