of the Chalk. 181 



sively, if he examine the two admirable preparations by Mr. 

 Goadby in the Museum of the Royal College of Surgeons, and 

 which exhibit sections, transverse and longitudinal, of the same 

 Alcyonium, he will perceive an arrangement of canals or tubes 

 bound together by an irregular network, and will at once perceive 

 that in no one point does this resemble the structure of the Ven- 

 triculidae, in which there are no tubes whatever*. He is thus 

 necessarily led to the same point, to which, by another means, we 

 have already arrived, though with less suggestiveness of the true 

 position of the objects before him. 



Starting then from that point, it must be always remembered 

 how much has been already determined as being essential in con- 

 tradistinction to any accidental or specific characters of these 

 objects f. It has been shown that they formed, — though soft- 

 bodied as distinguished from stony or from a toughly flexible 

 sponge-like mass, — a firm and enduring body, not contractile J, 

 and with a peculiar structure for maintaining its normal shape. 

 The variety of actual form under which they are found being 

 very great, it must be particularly remembered also that any 

 essential character dependent on any apparent tubules, external 

 or internal, is most distinctly and unequivocally negatived. Were 



description. It must be presumed that those generic characters have not 

 been assigned without a sufficiently extended observation, not confined alone 

 to British species. 



* I would refer to note, p. 186, for another marked and characteristic dif- 

 ference between the polypidom of the Ventriculidae and any of the Anthozoa. 



t Some, even shrewd observers, appear to find the greatest difficulty in 

 divesting themselves of the influence of ideas arising from mere general 

 external shape. This is extraordinary when there is no one branch of com- 

 parative anatomy, not to say natural history, in which its little importance 

 is not evidenced, and errors arising from it being daily exposed. They 

 point to the cupshaped sponges as so very like the Ventriculidae. I admit 

 a partial superficial likeness to some forms of Ventriculidae, but that is all. 

 And it may be a relief to such objectors to remind them of the external 

 form of several Polyzoa, e. g. Tubulipora patina, which is described by 

 Johnston, p. 267, as having a "polypidom like a little saucer: — it varies a 

 good deal in the deepness of its centre, for sometimes it is properly described 

 as being cupped, at other times it is so shallow that a saucer or plate becomes 

 the best object of comparison." There is a real analogy here to the external 

 form and habit of the Ventriculidae : and see the forms of T. truncata, T.peni- 

 cillata, &c, all much more like some Ventriculidae than any sponges are ; and 

 Milne Edwards points out a development of roots (ut ante, p. 211) which 

 forcibly recalls the Ventriculitic root. In the Museum of the College of 

 Surgeons there has been deposited, within the last few weeks, a most 

 superb coral from the Indian Archipelago which precisely resembles in its 

 general external form some of the more usual forms of the Ventriculidae. 



X In addition to the points before named, it seems obvious that the con- 

 tractile theory requires that the animal should be 6trictly a single and not a 

 composite one. It cannot be conceived that a polypiferous animal should 

 have its polypiferous surface contractile over itself. 



