106 Wisconsin Academy of Sciences, Arts, and Letters. 



Whether the smaller alveoli are really vacuoles in the same 

 sense as the larger openings mav be a matter of doubt. But 

 the fact that all o^rades in size can be found from the verr 

 small alveoli to the larger ones would seem to show that there 

 is no difference between them. In manv sections the smaller 

 "vacuoles appear to be fusing with larger ones. All stages may 

 "be made out from that in which the two adjacent vacuoles have 

 nearlv their oriainal spherical form to those in which the fusion 

 is almost complete and one appears as a slight protuberance 

 upon the other. The larger vacuoles above described often ap- 

 pear in turn to fuse with the central vacuole so that their mem- 

 brane becomes continuous with that of the central vacuole (Fig. 

 2). It is of course possible that tlie appearance of fusion of 

 the vacuoles just described is due to slight distortion in fixation, 

 for it can be readilv seen that if two vacuoles each surrounded 

 by a slight film, are lying very close together ; a very slight 

 disturbance in the protoplasm might cause a break in the films 

 so as to give the appearance of stages in the fusion of the 

 vacuoles. Still there seems to l)e no doubt that in the gro^\'th of 

 the cells from swarm spores the central vacuole is the result of 

 the fusion of two or more smaller vacuoles of the vouna: cell. 



While the above description of the relations of the larger and 

 smaller vacuoles seems to agree in many respects with what 

 Wilson (35) has recently descrilx^d for some Echinoderm 

 eggs, I have not been able to make out here any such morpho- 

 logical series consisting of granules, microsomes, alveoli and 

 vacuoles as Wilson described. Wherever the alveoli and vacuo- 

 les can be made out they seem to l)e quite distinct from the 

 other cell contents, and I am therefore inclined to think of 

 them as distinct cell organs perliaps in some respects coordi- 

 nate with such structures as the pyrenoids. Still if this 

 view be correct the question as to the origin of the vacuoles 

 is a perplexing one. The fact that smaller vacuoles may fuse 

 to form larger ones and that as a result of cleavage the 

 large central vacuole entirely disappears, would seem to 

 strongly negative the doctrine of De Vries (31) and Went 

 (34) that the vacuole is a permanent cell organ reproduced by 

 division of a preexisting vacuole. To be sure tlie vacuolar 



