of Ciivtei-eUn latiteuta, Putts. ■ 395 



Thus, as Noir(5 states in Max Milller's translation of Kant, 

 " Imagination is the greatest foe to true knowledge." 



As regards the general description and the spiculation of the 

 species of Spongilla which Mr. Potts has found in the State of 

 Pennsylvania (to which may be added one of Tuhella from 

 the Schuylkill river, just received), some of which do and 

 some do not bear the cirrous appendages, it is to be hoped 

 that one and all will be fully published with illustrations, as 

 the paucity of our information on the subject can ill afford 

 to lose a contribution like that which the indefatigable re- 

 searches of Mr. Potts, in one of the richest localities of the 

 world for Spongilla, have enabled him to supply. Why I have 

 apparently usurped a descri|jtion of the cirrous appendages 

 will have been made known by the above. 



Lastly, I would advert to Spongiophaga communis (one of 

 the many developments which, in these days of accounting for 

 every thing, has not been accounted for). What is it? and 

 whence does it come ? Abundant and common in Hir- 

 cinia, as before stated, " as the grass of the field," replacing 

 every part of the sponge but the inorganic skeleton so accu- 

 rately and so completely that at first sight it is impossible 

 to consider it otherwise, and yet so insidiously that it looks 

 like a transformation, I still' cannot help thinking that, 

 although we cannot identify the cirrous aj^pendages of the 

 statoblasts in Spongilla with it, yet they bear such a great 

 resemblance to SpongiopJuiga communis, especially in Carte- 

 rella tenospenna, that there is something analogous in the two 

 growths, whatever this may turn out to be hereafter. It 

 therefore must not be thought that because I have been obliged, 

 through further information, to abandon the generic appella- 

 tion Spongiopihaga for the cirrous appendages, I shall rest 

 Avith their discovery in Spongilla, any more than I did when 

 at first they appeared to me to throw some light on the nature 

 of Spongiopliaga communis. 



EXPLANATION OF PLATE XIV. 



N.B. — Figs. 2, 3, and 7-0 are drawn to the same scale, viz. l-48tli to 

 l-1800th inch, in order that the relative size of their several parts may 

 be at once realized. 



Fig. L Carterella Uditenta, Potts. Two statoblasts with their cirrous 

 appendatres, one bearing a single and the other a double cirrus. 

 About the natural size. Statoblast l-48th inch in diameter, 

 cirrous appendage about one third of an inch long. 



Fig. 2. The same. Cirrus single. Magnified upon the scale above men- 

 tioned, a, germinal contents of statobast ; b, membranous enve- 

 lope of the same ; c, chitinous coat (indicated by the dark line) ; 

 /I, apiculifenm.s coat (^indicated by the dotted line); r, maniil- 



