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develop and ripen in the body-wall of tlie animal instead of 

 in special buds or gonophores. Concerning the relationship 

 in this respect between Hydra and other Hydrozoa two 

 diametrically opposite views have been held, one being that 

 Hydra exhibits the simplest and most primitive condition 

 of the reproductive organs prior to the evolution of special 

 sexual buds; the other that the condition in Hydra is one 

 of extreme degeneration, the sexual buds that were pre- 

 viously present having completelj'- aborted. 



Quite recently Prof Weismann of Freiburg has published 

 some extremely interesting and valuable researches on the 

 development of the sexual products in Hydrozoa, and it is 

 the object of the present paper to enquire into the bearing 

 of these results on the problem stated above concerning 

 Hydra. 



In one of the typical hydroid colonies such as Podocoryne 

 or Bougainvillea the sexual products, whether ova or sper- 

 maldzoa, are contained in medusoid buds, and do not ripen 

 until these medusae have attained full development, and de- 

 tached themselves from the colonj" so as to lead a free- 

 swimming existence. In many cases, however, the sexual 

 products ripen before the medusoid bud has completed its 

 development, in which case the bud remains attached to the 

 colony in a more or less immature condition. In some in- 

 stances the gonophore is a fully-formed medusa, which, 

 however, never detaches itself from the colony, such a gono- 

 phore being called an attached medusa ; in other cases de- 

 velopment stops at an earlier stage, giving rise to a disguised 

 medusa, in which all the essential parts of the medusa are 

 present, but in an un expanded condition; and, finally, 



