101 The American Spongill^i. 



Mr. Bicknell says, " With Jampliglit and the condenser I can 

 resolve on Holler's Probe Platte (Type plate) up to and inclusive 

 Nitscliia curvula ; the Am. pelluclda having thus far refused to 

 show its lines."* The advancing power of the microscope is demon- 

 strated by the readiness with which Powell and Lealand show these 

 lines with their 1-1 6th and lamplight. Mr. Bicknell measures his 

 specimen at 87,000 lines only per inch. Powell and Lealand at 

 (1 think) about 100,000. But specimens vary very much in diffi- 

 culty and fineness. 



The Surirella gemma, ordinarily a line object, gives up beauti- 

 ful beads. In the photographs presented to me by Colonel Wood- 

 ward I counted with a pocket lens thirty heads, and carefully inserted 

 the points of a pair of fine compasses into the centre of i\ie first 

 and thirty-first bead so as to give the exact measurement of thirty 

 beads. This I found to be on Photograph xvii 



125 

 1 inch and tjj-^ or 1"*125. 



The power marked on the card was 3100 (probably by a clerical 

 error), which gives 



83,000 beads per inch, nearly. 



This appears rather too great. Fortunately the Colonel has sent 

 me two photographs of the same diatom. The larger is not qu:te 

 2^ times the sizej of the smaller. If therefore the magnifying 

 power employed be as stated upon the smaller one, 1034, the 

 second photograph is magnified not 8100 times, but 



2200 times, 



which gives nearly 



59,000 beads per inch. 



IV, — The American SjiongUla, a crasjjedote, flagellate Infusorian. 



By H. James-Claek, A.B., B,S., Prof. Nat. Hist., Kentucky 

 University, Lexington, Ky. 



Plate XI. 



The argument of Haeckel, and others, that the Sponges are essen- 

 tially compound Polypi, is virtually based upon the assumption 

 that the minor (afferent) and major (efferent) ostioles of the former 

 correspond to the mouths of the latter; and that the profusely 

 branching aff"erent and efferent canals of the Sponges are strictly 



* Page 71, No. xxxviii., this Journal. 



t Nearly as 347 to 162, by actual measurements. 



