vas tes Oper Hy paongar a Rise 5 acetates 
The Hydroidea are minute polyps of extreme simplicity Of 
structure and delicacy of form. Though sometimes single ani- 
mals swimming at large or attaching themselves at will, liket the Hy- ~ 
See Grant, Edinb: Phil. Jot xiii, xiv; Basgrdfa: Slag a ba Net., 5, 2d ‘e- 
ries, 1838, in which he endéavarito show, by minute microscopic researc, that 
they are compound infusoria ; Laurent, on the SpSngille, L’ a 1840, p 
231, 240, and the Microscop. Jour.,i, 78, who describes the reproductive. argialé 
of the supposed animals ; Hoge,on “thes Spongilla, Linn, Trans., xviii, 390, why 
sums up the results of his. investigations in the following language : —ée They have 
no tentacles, no cilia, no hep no @so ophagus, no stomach or gastric sac, no giz- 
zard, no Sinaiay ary cana nokintealine anus, no ovaria, no ova, no muscles or 
cular fibres, no hariie or ga gli, nd: irritability or powers of contraction and 
dilatation,, no 5 ae and no sensation whatever. Surely, then, we cannot 
’ liar to an animal, can be detected.” The existence of ova is placed beyond nih 
by the javddapations of Laurent; and these ova have animalcule-like motions 
when first produced. This fact has been considered decisive ; but as the spores of 
some Algz have similar life-like motions, this evidence alone is not satisfactory. 
| 
same composition as the fibrotn of silk—that is, the part of silk left after dis- 
solving out the gelatine and albumen. The sponge differs only in having the fi- 
broin combined with sulphur, iodine and phosphorus. It consists of carbon 48 01, 
ayerapen 6:35, nitrogen 16-06, oxygen 26-40, iodine 1:05, sulphur 0-46, phospho- 
tus 1-67. (Scheikundige Onderzoekingen, Deel ii, p. 1.) ‘This fact caraney 
sate weight to the side of the animal nature of sponges. . 
Judging from all the recent investigations, it may be received as most probable 
that sponges are the result of animal growth; that the minute component snide 
are more analogous to infusorial avitsajestes. = polyps} om they receive nies 
ment by absorption at the surface 
through a mouth; and owing to this simplicity of structure, the Pdinaoatity of 
‘the animalcules is nearly or quite lost in the general structure, just as the individ- 
uality of cellules in a simple growing animal is merged in ‘ the resulting organism ; 
d 
Of the: development ; wed essere —e from the surface of the general 
Structure, as in spon ges 
The limits of the two > kingdoms of ape the vegetable and the animal, are 
still i in Dore It would seem as if the two lines diverged from the same low 
nisms; for besides the moving spores - ‘Aiea, there are actual animalcules 
which are claimed by the wy on the ground that they act on the atmosphere 
like plants, giving out oxygen in ead of carbonic acid. Thea argument appears to 
; be good, oe the ving motions they present, and their complete re- 
