1886.] NATURAL SCIENCES OP PHILADELPHIA. 25 



METHODS OF DEFENSE IN ORGANISMS. 

 BY CHAS. MORRIS. 



Some weeks ago I presented a paper on this subject to the 

 Academy. I wish to add a few suggestions to the considerations 

 there taken, and particular!}^ to speak of the evolution of the 

 spOnge, considered from the point of view of defense. As is 

 well known, the sponge type of organism is one that it luis 

 proved difficult to classify, since it only partly conforms to the 

 type of the Coelenterates, while it is widely divergent from any 

 other animal type. I may briefly point out these divergent 

 features. 



In all other animals above the Protozoans, except those para- 

 sitic forms which are destitute of an intestine, the mouth is a 

 single aperture, which constitutes the main opening into the 

 boiy. In the sponge type this single aperture is replaced by a 

 multitude of minute openings, in connection with a single large 

 anal opening. In one other respect the sponge is different from and 

 more simplified than other animal types. Its digestion is 

 entirely cellular. It has developed no organ answering to the 

 stomach of other types. 



The sponge is, moreover, destitute of any organs of offense or 

 defense. Its nearest relatives, the polyps, have their tentacles 

 and thread-cells, in connection with a single aperture, which is 

 both oral and anal in function, and with a digestion which is 

 intermediate between the cellular and the stomachal methods, 

 and can be properly classed with neither. 



The method of obtaining food, by the aid of water currents, is 

 not peculiar to the sponge. It may be found in other animal 

 types, such as the bivalve mollusks, the Tunicata, Amphioxus, 

 etc. But in the sponge it is far more simplified than in these 

 higher forms. In the case of the mollusks, the water current is 

 confined to the branchiae, and only its food particles are taken 

 into the intestine. In the Tunicates and in Amphioxus respira- 

 tion is intestinal, but the water current is confined to the 

 branchial half of the intestine, while its food particles enter the 

 stomachal half, where they undergo digestion. In the sponge 

 the water currents permeate every portion of the body, and 

 respiration, as well as digestion, is a function of the separate 

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