REVIEWS. 
PONGES.* — Professor Heckel in this paper has condensed the results 
of an extended and very remarkable series of investigations with regard 
to the affinities of the Sponges. 
He places them nearest the corals, considering their canal system as 
hich however, springs from an originally cellular layer, and an inner 
cellular membrane. This comparison is carried so far that as in the 
Coelenterata (Acalephs and Polyps) the large vessel, hak conveys away 
the water admitted through the sides by the smaller branches permeating 
in proportion as they have one or more afferent openings. Of course Pro- 
fessor Heckel is well aware of the principal objections to his theory, and 
states them. The mouthless sponges, for instance, he accounts for by re- 
ferring to the mouthless Sycocystis, which, however, has young with a well 
formed mouth. The fact, however, that the water permeating the spon 
This cavity enlarging finally breaks through one end, and forms a oath 
opposite to the end which has already become attached to the rocks. At 
this young stage it is ign : be not essentially different nn. a fresh- 
water Polyp, or a young 
The author nowhere etis to the late memoir of Prof. H. J. Clark, the 
— vesicles and particles of food in various states of digestion. 
Carter’s observations, as well as Professor Hecke. distinctly confirm the 
edu. or single-haired, condition of the cells of the internal mem- 
brane, and the structureless, gelatinous nature of the external layer. 
fin tha f} 
ganizati f relationship to apd Corals, By Ernest M 
(T: lated in the Ann and Mag. : Nat. History Jan 1870, from 
207). 
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