VOL. XXIV.] PHILOSOPHICAL TRANSACTIONS. 15/ 



betake themselves to the bottom of the sea, as I am informed, but dig them- 

 selves holes in the sand, which secures them from being cast upon the beach or 

 strand : now if they had not eye-lids, the sharp points of sand, while they are 

 making their nest, would wound the tunics of their eyes, by which their trans- 

 parency would be destroyed, and the fishes become blind : which is a farther 

 proof how perfect every creature is in its own species. 



Concerning the Tubes or Canals that convey the yellow Sup in Aloes-leaves y &c. 

 By Mr, Leuwenhoeck, N° 293, p. 1730. 



I observed the external skin or membrane of the leaves of aloes, to discover, 

 if possible, of what tubes or pipes they were composed ; but was not able to 

 find out the conjunction of the parts; because that membrane was so weak and 

 tender, that it always broke without any remarkable discovery. I observed 

 that in the said membrane there lay as it were pressed in, roundish particles that 

 looted like little bladders, and in those little bladders, green particles, that had. 

 a sap in them ; and they lay as it were in a right line, and so interwoven with 

 each other, that they seemed to serve for tubes or canals. The impressions of 

 these round particles were in several places so regular, that each consisted of six 

 sides, disposed in the exactest order imaginable ; and in each particle might be 

 discovered a protuberance ; and they were separated from each other by rings or 

 circles, which I supposed to be the canals. 



I caused a small part of the forementioned hexangular particles to be drawn, 

 just as it appeared through the microscope ; as pi. 6, fig. 4, where some of the 

 canals, in order to distinguish them the better, are represented outwards, as 



at ABCD. 



On further examining into the aloes leaf, I discovered another sort of canals 

 or vessels, in which the sap appeared somevvhat reddish. Taking this sap out 

 of the said vessels, to try whether it contained any salt particles, and what figure 

 they were of; I let it stand a little, that some part of it might evaporate, and 

 the salts coagulate ; then placing some of it before the microscope, I observed a 

 great number of long, slender particles, that lay in the sap, and were sharp or 

 pointed at both ends ; and as I imagined that these long particles could not be 

 coagulated in so short a time as the sap was pressed out of the canals, but rather 

 that they were there before, I endeavoured to bring them out of the vessels, so 

 that there should come very little sap with them, that they might be seen and 

 drawn more distinctly ; a few of which (out of several hundreds that in a short 

 time I had heaped together) are represented in fig. 5, efgh. 



These slender particles appeared through the microscope very clear and trans- 

 parent ; 1 laid them upon a clean glass plate^ and viewing them about 3 weeks 



