j\Ir. H. J. Carter on the Suhsplierous Sponges. 15 



and horizontal sections of the crust in fresh, half, and wholly 

 di'ied specimens respectively of Pacliymatisma Johnstonia, 

 carefully made and manipulated under the microscope, taking 

 the precaution never to reflect the film of sarcode 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 the diaphragm 

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

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

 Barrett?, which had been " pickled 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 animals, and therefore that Dr. Bowerbank's 

 application of the term " membrane " to the dermal sarcode 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 parts of it 

 in the fresh state, and sometimes in the dried {ex. gr. the cortex 

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

 appears. 



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

 the lowest grades of animal life is not theoretically correct, 

 however much it may be desirable to do so for practical 

 purposes. 



We 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 uncrystallized, and 

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

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



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

 purposes we discom'se of those characters which are most 

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

 code 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- 

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

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

 at Bombay (Annals, Sept. 1856, vol. xviii. p. 242). The manu- 

 script was in the hands of the printer in England in the month 

 of June, and the first part published in the ' Annals ' on the 



