170 REPRESENTATION OF THE 



the former, that is, the sperm-sacs and ovisacs, which are 

 in due time developed in this matrix, as the true organs of 

 reproduction. In this view the medusoids of the Poly- 

 pifera, and other such sexual zooids, would differ in them- 

 selves from the organs of reproduction of the higher 

 species only by the greater complexity of their internal 

 structure, and the possession of certain appendages, required 

 for their maintaining an independent existence. 



4. In support of such a relationship reference may he 

 made to the reproductive organs of the Polyzoa, as occupy- 

 ing a position intermediate in some respects between that 

 of derivative gemmae, and that of mere organs of the par- 

 ticular polypes in connection wdth which they are developed. 

 Such at least is the view of Professor Allman. " If the 

 formation of the ovary," he remarks, " be attended to, it will 

 be seen that this body is developed at a later period from 

 the walls of the original sac-like embryo, which have Tinder- 

 gone slight changes and have become the endocyst [inner 

 coat] of the more mature Polyzoon, and it will be at once 

 perceived that this development of the ovary takes place in 

 a way which may obviously be compared with the forma- 

 tion of a bud, that at least in Alcyonella it occupies 

 exactly the position in certain cells that the buds destined 

 to become polypides [polypes] do in others, and that at an 

 early stage of polypide and ovary it is scarcely possible to 

 distinguish one from the other ; so that the idea is imme- 

 diately suggested that the body here called ovary is itself a 

 distinct zooid, in which the whole organization becomes so 

 completely subordinate to the reproductive function as to 

 be entirely masked, and apparently replaced by the genera- 

 tive organs. This would then constitute a third zooid, 

 which would therefore be a sexual zooid ; it is, however, 

 unisexual (female). Again, we find that upon the fimiculus 

 [or suspensory ligament of the stomach] there is developed 

 the mass described as testis. Now, if we view this mass 



