OLYNTHOIDEA. 591 



never afterwards can move. The rounded body soon becomes flattened, as it adheres with a 

 close grasp, and spreads itself into a nearly circular lilm. The cilia still exist on the upper 

 surface of this film, but the effect of their action is then not to propel the Sponge, but to 

 create a current of water which can pass over it. 



As time passes on, the distinctive spiculse become visible, and, after three weeks or a 

 month have passed away, the spiculse have been gathered into little bundles, which by their 

 arrangement tend to preserve the shape of the Sponge and to keep the orifices open. The little 

 being now spreads rapidly, by a process which much resembles the subdivision of the Infusoria, 

 and the whole mass of the Sponge is evidently composed of a vast number of the Amoeba -like 

 bodies which have already been described. Thousands upon thousands of these gemmules are 

 passed out into the sea from every Sponge that inhabits its waters ; and the only wonder is, 

 that, in consequence of such marvellously prolific properties, the Sponges do not swarm to such 

 an extent as to fill the whole seas, and poison the entire earth with the odor of their decay. 



THE editor of this edition would state here that though the Sponges were once regarded as 

 forming the lowest branch of the animal kingdom, as stated in the original text of this work, 

 they now constitute the second in the ascending scale, or next to the lowest, under the title 

 BRANCH II. PORIFERATA. As with other branches of the animal kingdom, we refer the 

 reader who desires to gain knowledge of the present state of science as applied to this branch 

 and that embracing the lowest animals, to the technical tables of classification and nomen- 

 clature of the Smithsonian Institution. Not long since, it is well known, they were so little 

 understood that no one had quite the courage to say which kingdom they belonged to 

 whether of the animal or vegetable. 



The present state of that section of science which refers to these low animals may be 

 simply presented as follows : It is now known, as the result of much study and observation 

 during the last ten or fifteen years, that the Sponges, in common with all other animals above 

 them, are composed of myriads of cells, 'which perform each their respective offices in the 

 animal economy. In some groups perpetuation by division of the body is observed. Yet in 

 all these are specialized cells or eggs, for the purposes of reproduction. 



In the first division of the animal kingdom, that embracing the lowest animals, and 

 called BRANCH I. PROTOZOA, it is observed that they differ by having only one simple cell ; 

 consequently they do not increase by means of eggs, but by division or segmentation. An 

 analagous example is seen when vegetable roots are perpetuated by cuttings. This difference 

 suggests to the naturalist two distinct divisions. Those animals having many cells are called 

 collectively METAZOA, and the single-celled PROTOZOA. 



Sponges are all aquatic ; found in the ocean, and in fresh water to a very limited extent. 

 They are all fixed, with very few exceptions, to some object near or on the bottom of the seas. 

 The young, during a short period, are supplied with cilia, by which they move through the 

 water until they become fixed. Myriads of floating microscopical plants and animals become 

 their food by absorption through the pores and open channels so characteristic of these forms. 

 The term Poriferata is selected to indicate this branch of animuls from this prominent 

 feature. The familiar vase form is characteristic of them. Some very beautiful examples are 

 familiar. 



The great Neptune's Cups are interesting forms, being complete vases in shape and con- 

 struction, yet in their native element living animal structures. 



Late authorities place Sponges as follows : 



Class I. CALCISPONG^E. Lime Sponges, literally. Yet all do not have the lime spicules 

 or skeleton framework of lime formation. 



Order I. An American representative of this order is known through Mr. J. A. Ryder's 

 observations, called CamarapJiysema. It is a club-shaped mass, with a tough exterior. 



Order II. OLYNTHOIDEA. This order embraces those forms that have the framework of 

 calcareous spicules. Some extremely curious forms of the latter are found, resembling arti- 

 ficial objects, as various forms of anchors, spears, "grains," etc. 



Four sub-orders embrace the comparatively few species of this order. 



