of the Organs f)/' Pilularia globulifera. 489 



of the growing' processes, for it is frequently in advance of them ; bnt it is pro- 

 dnced by a g'radnal condensation, inherent to the tissne, around the cavities 

 and along the radiating- dividing- lines, wliich, in fact, are nothing more tlian the 

 result of this condensation, which at maturity is so complete, that the whole of 

 the spongy tissne is condensed into four dissepiments, dividing the cavity of the 

 involucrum into four equal loculi (Tab. XXXV. fig. 30.). The nipple- like pro- 

 cesses are found upon a careful examination to be hollow sacs with obsciu-ely 

 cellular walls, those which occupy the lowest part of the involucrum being 

 considerably in advance of the upper ones. These sacs contain a quantity of 

 grumous matter, and a number — perhaps about ten — of soft, rather opake 

 pulpy bodies, which are evidently compounded of four closely connected parts, 

 so placed on each other as to form a cone with a triangular base (Tab. XXXV. 

 fig. 31 & 32.). These bodies have their future development in two different 

 ways, according, in a great measure, to the position they occupy in the involu- 

 crum. Those which occupy the upper portion, although not absolutely confined 

 to that portion, enlarge, become pellucid, and recede from each other, but con- 

 tinue to be attached to each other by four stalks as long as half their diame- 

 ter, which meet in one centre (Tab. XXXV. fig. 33.). It is now evident that 

 these four bodies or sporules are contained in a mother-cell, which most pro- 

 bably existed before, but on account of its close approximation to the four 

 united sporules could not be seen. On the surfaces of each of these sporules 

 are three short lines which radiate from the insertion of the stalk. From an 

 observation of the sporules of Isnëtes lacustris, I am inclined to believe that 

 these lines are a slight ridge caused by the projection of the membrane into 

 the interstices between the three other sporules, and that the stalk is a draw- 

 ing-out, as it were, of the same membrane, some evidence of which is seen in 

 the instance represented at Tab. XXXV. fig. 34. At length the mother-cell is 

 ruptured, and tiie sporules separate from each other at the point where the 

 stalks meet in one centre, so that each sporule is furnished with a short tail, 

 which, however, soon disappears (Tab. XXXV. fig. 34.). A deposit gradually 

 takes place on the outer surface of the sporule, forming a second coat, which 

 gradually becomes more and more opake, until the three radiating lines are 

 quite invisible, and the sporule a perfectly opake white body (Tab. XXXV. 

 fig. 36 & 36.). Until the sporules have become opake they are quite empty. 



