380 DR. ALLMAN ON THE ANATOMY AND PHYSIOLOGY OF CORDYLOPHORA. 
some of the free medusoids of a Syncoryne to be filled with ova, supposed these 
raedusoids to possess the same signification as that which Ehrenberg had attri- 
buted to the fixed capsules. Steenstrup, adopting with some slight modification 
the same view, has found in it one of the most striking of the facts which he has so 
skilfully collated in his essay on “The Alternations of Generations;” while \ax 
Beneden^, in two elaborate memoirs full of beautiful and accurate observations, has 
strenuously opposed it, maintaining that the ovigerous fixed capsules are mereh 
organs, ovisacs,” while the free medusoids are larvm destined to undergo a series 
of transformations during a process of development into the form of the parent 
zoophyte. M. Van Beneden, however, though he has had the medusoids long under 
his eyes, has never witnessed an actual development into the form of the parent 
polype, and the changes which he has figured as occurring in them do not appear to 
show any tendency to such a transformation. I have had the medusoids of a Syn- 
coryne for more than a fortnight under constant inspection without peiceiving the 
slightest change towards the form of the adult polype; at the end of this peiiod the\ 
perished. 
Dujardin'I' opposes the views both of Ehrenberg and Van Beneden, and taking 
the medusoids for true Medusoe, and viewing them even as distinct genera of Acalepha^ 
he generalizes the observed instances of their production, and maintains that the 
claviform polypes are universally only inferior phases of the development of the Acu- 
lepha ; while he considers the bodies produced in the fixed sacs onlj as bulbillte, 
by which he understands gernmm, which become detached at an early stage, and are 
then capable of an independent development. The strong resemblance however 
between true Medusce and the medusoids produced by a process of gemmation from 
polypes does not afford sufficient grounds for maintaining that all Medusce are only 
advanced stages of tubularian zoophytes and of Campanularice, or that all these 
zoophytes are only earlier phases in the development of 3Iedusce ; and M. Dujardin’s 
generalization, from which would result the complete abolition of the Campanularia^ 
and tubularian zoophytes as distinct groups of the animal kingdom, is certainly 
destitute of sufficient foundation, while the bodies contained in the fixed sacs aie 
undoubtedly not gemmce but ova, as their structure and the whole history ot their 
development must render evident. I cannot think, then, that either Van Beneden 
or Dujardin has succeeded in overthrowing the theory of Ehrenberg. 
The conclusion to which the facts sought to be demonstrated in the present paper 
would seem to lead, is that in the tubularian zoophytes there exist three kinds ot 
zooids, all produced by a process of gemmation from an original stolon, wdiich is itselt 
the immediate product of a true ovum. These are, — 1. the ordinary terminal 
* Mem. sur les CampaBulaires, and Recherches sur I’Embiyogenie des Tubulaires, Nouv. Mem. de 1 Acad. 
Roy. de Bruxelles, t. vii. 
t Dujardin, Sur le Ddveloppement des M6duses et des Polypes Hydraires, Ann. des Sci. Nat. 3'“ sdr. t. iv. 
1845. 
