390 MR. R. OWEN’S REMARKS ON THE ENTOZOA. 
effected by reciprocal intromission. Again, distinct sexes are attributed to the Echino- 
rhynchi, the highest organized of the Parenchymatous Intestinal Worms. 
Thus the generative system fails to afford a character applicable to the whole of the 
Acrita of Mr. MacLeay; and we are equally unable to predicate of them a simple diges- 
tive sac without an anal outlet. In general it may be observed, that it is only with 
respect to the nervous system that we can attribute a community of structure to a pri- 
mary division of the animal kingdom. 
Now the classes which present the diffused condition of the nervous globules, are the 
Polygastrica, Spongie, Polypi, and Acalephe ; to which must be added the Vers Intesti- 
naux Parenchymateux of Cuvier, or Vers Mollasses of Lamarck, and of which I would 
propose to form a class of Acrita under the term Sterelmintha'. 
But as all the classes of the Acrite division exhibit the lowest stages of animal orga- 
nization, and are analogous to the earliest conditions of the higher classes, during which 
the changes of the ovum or embryo succeed each other with the greatest rapidity, so we 
find that the species in each class successively present modifications of their peculiar 
types, which come into close approximation, not with the Acrite classes immediately 
succeeding them, but with some one or other of the classes of higher groups in the 
animal kingdom, of the typical form of which the Acrite classes represent, as it were, 
the germs. Owing, therefore, to this tendency to ascend in the Acrita, it becomes pro- 
portionally more difficult to assign a general organic character to that than to any of 
the higher divisions. Even with respect to the nervous system we find, as we are led 
step by step from the Hydra to the Actinia in the class Polypi, that the nervous glo- 
bules begin to manifest the filamentous arrangement about the oral orifice of the last- 
named genus; that in passing through the Sterelmintha from the Hydatid to the Echi- 
norhynchus, we come also to perceive traces of longitudinal nervous chords in that 
highly organized Entozoon ; and that in the Acalephe, examples of the aggregate form 
of the nervous system have been described. But even supposing these exceptions to 
be well founded, and the filaments to be really nervous which have been so considered’, 
yet the proportion of each class in which the molecular diffused condition of the nervous 
1 Srepeos, solidus, éApurs, a term applied by the ancients to intestinal worms, which were distinguished into 
pubes orpoyyvdat, or Intestinalia teretia, and éhpw Hes wharerat, or Intestinalia lata. My compound is 
further sanctioned by a term invented by Zeder for the Entozoa generally, viz. Splanchnelmintha, which term 
is, however, with that of Entozoa, equally subject to the objection of being applied to animals of different classes 
according to structure. 
2 Professor Ehrenberg has recently ascribed to the Medusa aurita distinct visual organs, in the form of minute 
red points, situated on the surface of the eight brown-coloured masses set round the circumference of the disc. 
These masses consist each of a yellowish, oval or cylindrical, little body, which is attached to a small and deli- 
cate pedicle. This short pedicle arises from a vesicle, in which there is placed a glandular body, unattached, 
presenting a yellow colour when viewed with transmitted light, and a white colour when under reflected light. 
It is on the dorsal aspect of the yellow head which surmounts the pedicle that the well-defined red spot is seen 
which Professor Ehrenberg considers as an eye. He compares the eyes of Meduse to those of Rotifera and 
Entomostraca. The glandular body situated at the base of the pedicle, he regards as one optic ganglion, which 
