REJUVENESCENCE IN NATURE. 26*9 



During the time they are in motion, the gonidia exhibit 

 a longish shape, in the transition to rest they re-acquire 

 the original globular form. The rest is followed im- 

 mediately by germination. All these processes, from the 

 formation of the clubs to the swarming out of the gonidia, 

 are the work of a few hours.* The occurrence of large 

 resting spores, which has escaped most observers, f is a 

 normal phenomenon in the later period of the existence 

 of Saprolegnia, occurring sometimes simultaneously with 

 the formation of the gonidia, usually, however, after that 

 is terminated. The spores are formed in globular or 

 pear-shaped, expanded cases, at the tips of slender 

 divaricated lateral branches ; the tips of the erect shoots 

 more rarely swell up into such bulging spore-cases. In 

 exceptional cases spores are formed also in cylindrical 

 terminal tubes, agreeing in form with the gonidium- 

 cases. The mode of formation of the spores agrees in 

 all essentials with that of the gonidia. The granular 

 mucilaginous contents of the future spore-cases become 

 darker and more opake than those of the gonidium-clubs, 

 but, as in them, become applied upon the wall of the cell. 

 In this stage several large vesicles, arranged at regular 

 distances, make their appearance in the dark mass of the 

 mucilaginous layer. 



When we compare the number and distance of these 

 vesicles with those of the future spores, it scarcely admits 

 of doubt that they are nuclei, from which proceeds the 

 formation of the spores, especially since we may often 

 distinguish a similar lighter vesicle in the developed 

 spores. The formation of nuclei is followed by the 

 production of elevations on the internal surface of the 



* The statement of Meyen, (' Pflanzen-physiologie,' iii, p. 457, 1. 10, f. 19,) 

 that the active gonidia are formed in separate mother-cells inside the club, is 

 incompatible with my observations. Perhaps the key to this difficulty lies 

 in the above-mentioned observation that the gonidia of Saprolegnia capttuli- 

 fera acquire a membrane shortly after birth, (see p. 188.) It is conceiv- 

 able that Meyen's observation was made on another peculiar species in 

 which the gonidia acquire a membrane even before birth. 



f I find it mentioned only by Schleiden, (' Grundz.,' Ite Aufl., ii, p. 36.) 



