54 Bibliogrnphical Notices. 



we have to chronicle one of not less consequence on the Freshwater 

 Sponges, viz. that the title of which heads this article. 



Of this contrilution we must observe in limine that having been 

 published in the pages of a scientific journal shows that it is not 

 to be regarded as written for pecuniary emolument, but rather as a 

 " labour of love," which, when backed by the enthusiasm of a hoyid 

 fide naturalist (that is, an ardent desire to pursue truth and nothing 

 but the truth), guarantees a result that in this respect is seldom 

 equalled by one undertaken for mere pecuniary remuneration. 



The ' Monograph ' embraces all of any consequence that has been 

 published up to the present day, and much more that has not been 

 published at all, which has been obtained by Mr. Potts from 

 the abundance of species and varieties of Freshwater Sponges 

 existing in the neighbourhood of Philadelphia, where he would 

 appear not to have " left a stone unturned ; " while in all other 

 instances he has possessed himself of actual specimens of the species 

 or varieties described before putting pen to paper ; so that with this 

 determination to state nothing but what has been confirmed by his 

 own ocular demonstration, he has produced a work that must be one 

 of reference for a long time to come. 



In qiiotations, where possible, Mr. Potts prefers the exact words 

 of the author, and only where absolutely necessary substitutes con- 

 densation ; while references to titles, dates, &c. accomjjany every- 

 thing that he has stated ; so that in this matter Mr. Potts has been 

 as scrupulously careful as in his identification of the species described 

 by means of actual specimens. 



The plan of the ' Monograph,' after a list of " Contents " and a 

 " Preface,'' is to begin with a few words of elementary information, 

 *' to aid those who for the first time undertake the study of Sponges,'^ 

 in which many useful hints will be found that were suggested to the 

 author during his numerous excursions in search of Sj)ongidoe. 



Then comes the translation into English of a valuable paper 

 (originally written in German) by Prof. F. Vejdovsky, of the Uni- 

 versity of Prague, entitled "Diagnosis of the European Spongillidre," 

 which was drawn up at the request of Mr. Potts, as his own per- 

 sonal experience had been chiefiy confined to North America ; but 

 although this adds greatly to the value of the work, the author tells 

 us that he has found it most convenient to follow in his descriptions 

 the more general classification proposed by Mr. Carter, introducing 

 his own «f?(' genera, species, and varieties in their approj^ri ate places 

 as he proceeds. 



And in this part (which forms the bulk of the ' Monograph ') it 

 is that we see what an immensity of time and labotir the author 

 must have bestowed on his subject both in compilation and actual 

 research. Here the result of that indomitable perseverance appears 

 which could only arise from an enthusiastic love for the work and a 

 conscientious deteimination not to put forth anything but that which 

 would be a safe guide to the young and inexperienced student. 

 While in his concluding remarks he observes that in closing his 

 ' Monograph ' " it is with the consciousness that the work of classi- 



