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 gi-eater 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 be 

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

 ing a position intermediate in some respects between that 

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

 ticular polypes in connection with which they are developed. 

 Such at least is the view of Professor AUman. " 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 under- 

 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 i^j 

 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 w^ould therefore be a sexual zooid ; it is, however, 

 unisexual (female). Again, we find that upon the /"Mmcz^/w^ 

 [or suspensory ligament of the stomach] there is developed 

 the mass described as testis. Now, if w^e view this mass 



