Mr. IT. J. Carter on the Suhspherous Sponges. 15 



and liorizontal sections of tlie crust in fresh, half, and wlioUy 

 dried specimens respectively of Pachymatisina Johnstoniaj 

 carefully made and manipulated under the microscope, taking 

 the precaution never to reflect the film of sarcodc which lines 

 the cavities under examination, as this at once destroys all 

 certainty respecting the apertures which may or may not exist 

 in them in their intact state. 



One point, however, I. would notice, viz. that I have not 

 had an opportunity of seeing the aperture in tlie diaphragm 

 open and close as stated by Dr. JJowerbanlc, which statement 

 must have been an inference, as it refers to a specimen oiQeodta 

 Barreiti^ which had been " })ickled in strong salt and water " 

 (Phil. Trans, p. 1099). 



I have stated that, at this early period of animal develop- 

 ment, we should not expect to find tissues of the same kind as 

 those in higher aninuils, and therefore that Dr. Bowerbank's 

 application of the term "membrane" to the dermal sarcodc is 

 not legitimate. But although the whole of the soft substance 

 of the sponge on drying becomes agglutinated into a homo- 

 geneous mass like glue, there are frequently many ])arts of it 

 in the fresh state, and sometimes in the dried {tx. (jr. the cortex 

 of Tethya lyncurium &c.), where tissue-like structure faintly 

 ap})ears. 



To deny, therefore, the presence of tissues in the sarcodc of 

 the lowest grades of animal life is not theoretically correct, 

 however much it may be desirable to do so for practical 

 purposes. 



Wc cannot see the elements of which water or glass is 

 composed, but inference leads us to the conclusion that the 

 one IS formed of particles of matter in an uncrystallizcd, and 

 the other in a crystallized condition. Indeed, if we could sec 

 either in either state, there would be an end of all microscopy. 



All we know of things is by comparison, and for practical 

 })urposes we discourse of those characters which are most 

 familiar to our senses; still we cannot help seeing in the sar- 

 codc of the sponge a looming of tissues which, like objects 

 approaching from a distance, become more evident to us in 

 the coarser, more durable, and more evident developments of 

 the higher animals. 



But, to return to Dr. Bowerbank's " true pores," which I 

 have, in my description of the '' Ultimate Structure of Spon- 

 (jilla'''' (Annals, 1857, vol. xx. p. 21), designated " apertures" 

 of the investing membrane. These I discovered in 1856, while 

 at Bombay (Aniuds, Sept.l85G, vol. xviii. ]). 242). The manu- 

 scri])t was in the hands of the ])rinter in England in the month 

 of June, and the first ])art published in the ' Annals ' on the 



