DR. ALLMAN ON THE ANATOMY AND PHYSIOLOGY OF CORDYLOPHORA. 381 
zooids, on which devolves more especially the function of the reception, digestion, 
and elaboration of the nutrient material ; 2, the fixed reproductive zooids, in which 
every function is rendered subordinate to the production and development of the ova 
or spermatozoa, and in which a medusoid structure is more or less disguised ; and 
3. the free medusiform zooids, in which a complete medusoid structure is obvious. 
The office of these last is less exactly determined than that of either of the others ; 
sexual reproduction is probably, as in the fixed reproductive zooids, their characteristic 
function ; for as we have already seen, they have in several instances been found to 
contain ova ; yet in the greater number of cases no ova have been detected in them, 
and observations are still wanting to enable us to decide whether at one period or 
another of their existence a true generative office is not, under favourable circum- 
stances, always performed by them. It is certain that the other functions are not 
here so completely subordinated to reproduction as in the fixed sacs, for since the 
medusoid has become entirely detached from the parent, a more elaborate organiza- 
tion is necessary to enable it to maintain an independent existence. Uniting the 
functions of reproduction with extensive locomotive powers, it is probably destined 
to carry the ova to a distance from the parent stock, and thus provide for the disper- 
sion of the species, for the motion of the ciliated embryo is too slow to be of any use 
in this respect. In the CampanularicB^ besides these three forms of zooids there exists 
a fourth, in which the medusoid structure is also obvious, though not so completely 
developed as in the free medusoids ; the bodies belonging to this group remain per- 
manently fixed at the mouth of the capsule ; their function is that of true sexual 
generation, and after giving birth to ova or spermatozoa they wither away. The 
ovigerous sacs of degraded medusoid structure concealed in the interior of the cap- 
sules of Campanularia are quite different from these, and belong to the second kind 
of zooid enumerated above. In Sertularia and its immediate allies no locomotive 
zooids have as yet been found, and the generative zooids of Sertularia argentea 
already described admit of comparison rather with the fixed medusoids attached to 
the mouth of the capsule in Campanularia, than with the ovigerous sacs of the Tiihu- 
lariadae. 
It would seem then that Ehrenberg struck upon the true determination of the 
ovigerous sacs in Coryne when he called them ‘‘ female polypes,” though he erred 
when, supposing the “ovarian vesicles” of Campanularia to be the homologues of the 
ovigerous sacs of Coryne, he called these vesicles also by the same name ; the true 
homologues of the reproductive sacs of the Tuhulariad<je being, not the external cap- 
sules of the Campanularice, but fixed bodies with a disguised medusoid structure 
contained in the interior of these capsules*. 
The present state of our knowledge of the Tubularian and Sertularian polypes 
would seem to justify the generalization, that for the production of ova in tliese 
* Krohn has already pointed out that the capsules in Campanularia have a signification different from that 
of the ovigerous sacs of Coryne, 1. c. 
