REVIEWS. 361 



external surface immediately below the apex exhibiting no subsequent adhesive 

 property. 



" Lehman, in his ' Physiological Chemistry,' Cavendish Society's edition, vol. I. 

 p. 401, states that Spongia officinalis of commerce consists of 20 atoms of fibroin, 

 1 atom of iodine, and 5 atoms of phosphorus ; and in treating of the physiological 

 relations of fibroin as regards sponges, he observes: 'Its chemical constitution 

 afibrds one of the arguments why tbe Spongia should be classed among animals 

 and not among plants, since in the vegetable kingdom we nowhere meet with a 

 substance in the slightest degree resembling fibroin.'" 



Elsewhere he enumerates the following nine varieties of keratose 

 skeleton fibre : 



1. Solid simple keratose fibre. 



2. Spiculated keratose fibre. 



3. Hetro-spiculated keratose fibre. 



4. Multi-spieulated keratose fibre. 



5. Inequi-spiculated keratose fibre. 



6. Simple fistulose keratose fibre. 



7. Compound fistulose keratose fibre. 



8. Regular arenated keratose fibre. 



9. Irregularly arenated keratose fibre. 



"We cannot here enter at length on Dr. Bowerbank's speculations res- 

 pecting the sarcode substance of sponges. He considers it as not merely 

 the principal material of the body of Protozoa, but as closely related 

 (if not identical) to the mucous lining of the intestine in the higher 

 animals and the corresponding substance throughout the animal king- 

 dom, but he views it as a whole as the most vital portion of each 

 sponge. "We have already stated our belief that we are to consider 

 each insulated sarcode cell as an animalcule and the mass of the sponge 

 as a great colony, the membranes and hard parts of which are to be 

 compared with the common parts of Hydroids among Acalephae, and 

 of such Polypifera as Aicyoniums and Gorgoniads. According to this 

 view the individual animalcule differs from an Amaeba in being a cell 

 enclosed by a membrane and nourished by absorption, and hence we 

 denominate the class as animals living by absorption, and in the division 

 of the Protozoan subkingdom which onlj admits of the lower three 

 out of the five tendencies of development observable in the animal 

 kingdom, we place this class as second of the three, or as correspond- 

 ing to the fourth position in which an anomalous mode of obtaining 

 food, frequently suctorial or extractive, is a characteristic. We do 

 not apprehend that this difference as to the theoretical nature of a 



