McCrady.] 184 [Dec. 3, 



highly specialized structure) is equally unsupported by all we know 

 of development, and utterly incongruous with the known processes of 

 gemmation among the Hydroid Medusae. 



But the fact that Cunina is, during its larval existence, a parasite, 

 deriving its nourishment from the stomachs of other Medusse of vari- 

 ous forms, various genera, various families, and even various orders, 

 such as Aegina, Liriope, Carmarina, and Turritopsis, and taking such 

 positions either within or without the stomach, as will render it pos- 

 sible to procure the food there elaborated, is important as multiplying 

 the evidences that parasitism is not confined to any particular class or 

 group of special animal forms ; and that we must recognize not only 

 parasitic Insects and Arachnida, parasitic Crustacea, parasitic Gaste- 

 ropoda, parasitic Worms, and parasitic Actinias, but that the habit of 

 parasitism is not even foreign to the class of Acelephse. Parasitism is 

 indeed the universal condition of finite existence. 



The special connection of this discussion with my present subject 

 is, that the analogies of Bucephalus with the Hydroids, remote as 

 they are, have led me to reflect that Leukart's Coelenterata have 

 been very much neglected in the general movement of recent sys- 

 tematists to revive the simple classification of our ancestors, and 

 to incorporate all the low forms of animal life in the all-embracing 

 group of Worms. The typical Hydra itself is remarkably vermiform, 

 and so also are many Ctenophorse, and there is not a single Aca- 

 leph or Polyp which is not equally or more vermiform than any single 

 Echinoderm. Yet the naturalists, who have not been deterred by 

 the enormous difficulties of the case, from favorably entertaining 

 Huxley's proposal to associate the Echinoderms with the Annelides, 

 have not hesitated to leave the Coelenterata behind. But certainly the 

 movement in question cannot be complete until the great sub-kingdom 

 of Worms has absorbed into itself not only the Annelides, Kotifers, 

 Gephyrise, Platyelminthse, Nematoda, Polyzoa, Brachiopoda, Tunicata 

 and Echinoderms, but these much overlooked Acalephse and Polypi. 

 These last are not only fully as vermiform as the Echinoderms, but 

 the Hydroids and Discophoree have, in their planula form and its 

 modifications, a vermiform embryological basis, which has no radiate 

 characters. There is a stage more or less vermiform, succeeding the 

 egg stage, in nearly all animals. Well marked indications also of 

 bilateral symmetry have been pointed out by various observers 

 throughout the groups of Polypi and Acalephse. The general absence 

 of an anus is no objection, for besides the differentiation between the 



