Observations on Saprolegniece. 143 



As may be already inferred, there is attributed to this genus, 

 as to the others noticed, an alternation of generation. I have 

 not been able to give the parthenogenetic form a very thor- 

 ough study, but in two experiments w^hich occupied twelve 

 or thirteen days, sporangia, much resembling the late forms in 

 Saprolegnia, were produced. They were later than the oogonia, 

 and borne on shorter filaments which radiated from the fly. 

 The oogonia are produced in great abundance at irregular in- 

 tervals on different sides of the filaments, very seldom appear- 

 ing terminal. They are developed in a similar manner to the 

 oogonia of Achlya racemosa, var., smaller, being from .04 mm. to 

 .05 mm. in diameter, and the contents are more densely granu- 

 lar; the pedicel is as small in proportion to the oogonium as 

 in A. polyandra, but generally larger and curved its whole 

 length, giving a drooping character to the organ (Plate VTI., 

 Fig. 5). The oogonium membrane is pierced by many holes 

 (Fig. 21) — a provision for the aid of fertilization — in which 

 respect it differs from M. sphcerica, Cornu, and M. po/ymorp/ia, 

 Cornu (2, Plate II.), for to these species is attributed a single 

 opening at the extremity of the oogonium. The greatest dif- 

 ference from the sexual generation already described, rests 

 in the development of the male organ, which is ultimately a 

 free body, formed from the side of the oogonium instead of 

 its pedicel, and seldom fertilizing the one from which it is 

 produced. 



When the oogonium has nearly reached its full size, there 

 appears a small swelling on its side, generally near the pedicel. 

 This projection increases to form a nearly spherical mass, of 

 about one-fifth the diameter of the oogonium, and filled with 

 granules of varying sizes, though not as dense as the oogoni- 

 um. Whether this body was formed by a projection through 

 an opening already existing in the outer membrane or not I 

 cannot definitely say, but think it highly probable, for the 

 place of attachment is about the size of some openings noticed, 

 and its membrane is delicate like the inner membrane of the 

 oogonium. It reaches its full size (Plate VII., Fig. 5) in about 

 seven hours, when it is separated from the contents of the 

 oogonium by a diaphragm, and in two hours more a lightly 

 granular protoplasmic body bursts through the top of this 

 lateral cell, escaping free into the surrounding medium (Plate 

 VII., Figs. 6 and 7), leaving a transparent delicate sac attached 



