490 E. A. MINCHIN. 



not have seen, or what his views may have been at one time 

 or another, as to the nature of these or other cell elements. 



The last author who, so far as I am aware, lias described 

 the porocytes is Topsent (1892). In the same year (1) I had 

 published some observations far from complete upon the 

 histology of '' Leucosolenia ^' coriacea, amongst which I 

 had figured and described the contracted porocytes in sec- 

 tion, but had wrongly interpreted them as the amoebocytes or 

 '' cellules digestives pigmentees " of Topsent. In criticising 

 ray observations Topsent rightly pointed out my error, and 

 gave a good and accurate description of the porocytes, but 

 without himself arriving at a true understanding of their 

 nature. He terms them '' cellules spheruleuses du meso- 

 derme," in distinction to the amoebocytes or "cellules granu- 

 leuses du raesoderme,'^ and considers that tiiey represent 

 reserves of nutriment. He was guided to this interpretation 

 from the reactions of their granules. It is by no means im- 

 possible that the cells in question should combine the functions 

 of storing reserve nutriment with that of acting as pores, but 

 I certainly cannot agree with Topsent in regarding this as 

 their sole function. I feel quite convinced that if he had 

 compared them in the expanded state with the contracted con- 

 dition in which he figures them, he would have agreed with me 

 in my interpretation of them as closed pore-cells simply ; for 

 that his drawings do represent contracted material is shown 

 by internal evidence. The appearance of the " ectoderme " in 

 his figs. A and b as compact masses of granules at considerable 

 distances apart is exactly the appearance it shows when con- 

 tracted. Moreover in the surface view a not a single pore is 

 shown ; but a piece of this size, if expanded, would contain at 

 least half a dozen pores (compare PI. 38, fig. 10). Topsent 

 remarks, in his criticism on my work, that I had only been 

 moderately struck (" mediocrement frappe ") by these very 

 conspicuous cells ; but that is simply because my material was 

 all preserved immediately when found, and as a result the 

 pores were found expanded, and described by me as such, 

 except in one specimen which was contracted when found, as 



