1848.] LONSDALE ON FOSSIL ZOOPHYTES. 61 



in some specimens (pi. 1. figs. 7, 8, pi. 5. fig. 1) more the larger 

 openings of ordinary corneous sponges than of those in Manon, while 

 in the "adult" variety (pi. 29. fig. 8) they exhibit peculiarities not 

 easily assignable to the specimens just noticed ; and in the example 

 delineated in pi. 34. fig. 8, they are as well circumscribed and simple 

 in nature as in M. tiibuliferum or M. marginatum (pi. 34. fig. 9). 

 Lastly, it would be difficult to separate generically M. pirifoi-me 

 (pi. 65. fig. 10) from Siphoniajicus (pi. 65. fig. 14) or S. punctata 

 (fig. 13), the slight central depression marking probably nothing 

 but a very aged condition. These observations, though limited to 

 one or two characters, and derived solely from figures or descriptions, 

 justify, it is conceived, the belief that the fossils assigned in the work 

 quoted to Manon, possess great diversity of characters, and require 

 long study by a skilful physiologist before their true nature can be 

 rightly understood. It may however be stated, that no structural 

 agreement with the Atherfield fossil could be detected in any in- 

 stance ; and a comparison of the specimens examined with M. Roe- 

 mer's delineations of the genus {op. cit. pi. 1) will satisfy the ob- 

 server, that in those cases likewise there is no identity of composition. 

 3. The characters assigned to Achilleum by Goldfuss are, *' stirps 

 polymorpha, affixa, e fibris reticulatis lacunosa" (p. 1) ; and Herr 

 Roemer states, that the polymorphous bodies consist of a trelhs of 

 round or straight fibres with knots at the junction-points ; and that 

 they have no special apertures {op. cit. p. 2). M. de Blainville passes 

 over the genus in silence (Man. d'Act. p. 530) ; and M. Milne-Ed- 

 wards, adopting all the species retained by Goldfuss, conceives '* qui 

 paraissent etre des eponges proprement dites" (Lamk. ii. p. 5/6). 

 The structures on which the genus is established deserve great atten- 

 tion — a simple network without any special apertures. Dr. Johnston 

 says, " Many sponges are entirely destitute of oscula" (Brit. Sponges, 

 p. 13) ; but it must not be inferred from this expression, that excurrent 

 streams are denied in those cases*. On the contrary, the seeming 

 absence of such openings should lead to a careful research respecting 

 the means by which their functions are performed ; and new data for 

 accurate determinations may result from the inquiry. Dr. Grant has 

 satisfactorily shown the manner in which the want of scattered oscula 

 is compensated in Grantia compressa by the great central cavityf ; 

 and the necessity in certain species of Halichondria for their general 

 distribution;};. He has likewise successfully combated the opinion, 

 that water may be imbibed and ejected through the same oscnlum in 

 ordinary sponges §. Should bodies apparently allied to Amorphozoa 

 be discovered, in which the twofold operation is performed through 

 one aperture, then it will become necessary to propose for their re- 



* Consult Dr. Grant's Memoir on Sponges, Edinb. Phil. Journ. vol. xiii. p. 334, 

 and vol. xiv. p. 117, 1825-6. 



t Ed. Phil. Journ. vol. xiii. p. 334 ; Lectures, Univ. Coll. Lond. ; Lancet, vol. i. 

 1833-34, No. 531. p. 199. 



+ Ed. Phil. Journ. vol. xiii. pp. 106, 334-5 ; also Todd's British Annual for 1838, 

 p. 267, fig. 2. 



§ Ed. Phil. Journ. vol. xiii. p. 105-107, p. 333 et seq., vol. xiv. p. M7 et seq. 



