ACHLYA AND SAPROLEGNIA. 



antheridium from the filament it contains a small but variable number 

 of nuclei. These nuclei undergo the same changes as those in the 

 oogonium, i. <?., they divide karyokinetically, and some disorganize. 

 The fecundation-tubes are now developed and usually more than one 

 from each antheridium. They penetrate the wall of the oogonium at 



FIG. 37. Stages in development of sexual organs of A. ameri- 

 cana var. cimbrica. (After Trow.) 



A, young oogonium before delimination from hypha; base 



of globular enlargement incloses a vacuole which is con- 

 tinued back into hypha. 



B, much later stage ; an antheridium applied to oogonium, 



both organs delimited fromhyphae; protoplasm of oogo- 

 nium, which now forms a thick wall-layer, has begun to 

 ball up to form the eggs. 



C, still later stage ; balling more pronounced. 



D, oSgonium with differentiated eggs ; conjugation-tubes from 



applied antheridium have entered oSgonium and become 

 applied to some of the eggs. 

 A-D drawn from living material. 



the thinner places or pits, and grow in among the eggs (Fig. 37, D, f. t.). 

 These tubes contain nuclei which are exactly like those of the eggs, 

 though smaller. In one case Trow was able, as he states (99, p. 159) 

 to trace the fecundation-tube without a break into an egg which was 

 already surrounded by a delicate membrane (Fig. 38, C). This 

 instance "suggests that the fertilization-tube grows up to the egg, 

 presses against it, indents it, stimulates it to the formation of a cell-wall, 

 and grows obliquely into the mass of protoplasm, carrying at its apex 

 a single nucleus (Fig. 38, C). . . . Later stages tend to show 

 that the wall of the tube within the oosphere breaks down, the nucleus, 



