ELISHA MITCHELL SCIENTIFIC SOCIETY. 3 1 



posed of surfaces, has not beeu alluded to, as it is not now found in auy 

 text-books. It is an exploded theor\\ Cavalieri, the author, was led to 

 it by noticing, e. g., that in fig. 2, area APQB was never exactly equal to 

 area APSB; hence he made ax = and regarded the area a^/ as a line 

 AP, so that tc = area CDPA was made up of an infinity of lines, etc. 

 This is analogous to the statement that a variable can reach its limit. 



In conclusion, let us hope that soon, the false conceptions 

 concerning the fundamental principles of the calculus may 

 be eliminated from all text-books. The world is still 

 waiting for the treatise on the calculus that is simple and 

 clear and at the same time rio^orous in its lomc. 



REMARKS ON THE GENERAL MORPHOLOGY OF 

 SPONGES.* 



BY H. Y. WILSON. 



I haYC shownt that in Esperella and Tedania the sub- 

 dermal caYities, canals and chambers develop as separate 

 lacunae in the parenchyma or mes-entoderm of the attached 

 sponge, subsequently becoming connected into a continu- 

 ous system. As regards the development of the canal sys- 

 tem such varying accounts are given by different authors 

 that were it not for the help lent by comparative anatomy 

 it would be quite impossible to form any idea of the fun- 

 damental morphology of sponges. Fortunately for the 

 student entering this puzzling domain comparative anatomy 

 has, in the hands of Haeckel, Schulze and Polejaeff, pro- 

 vided a stand-point from which the varying phenomena of 



*These remarks were originallj' written as part of a paper on the embrj-olog-s- of 

 sponges, which it is expected will soon go to the press. It has not been fonnci possible 

 to insert in the present text the wood-cuts with which the intention was to illustrate 

 man J' of the facts referred to. The omission of the cuts, while it is to be regretted, 

 will not be found to interfere with the intelligibilitj- of the views expressed. 



fXotes on the Development of Some Sponges. Journal of Morphology-, Xo). V, No. 3. 



