272 SUMMARY OF CURRENT RESEARCHES RELATING TO 



spores the protoplasm may bo distributed in tbo sporangium in threo 

 different ways, viz. (1) the wbolo of tbo sporangium is filled with pro- 

 toplasm ; (2) the protoplasm forms a parietal layer of the same thickness 

 as the height of the subsequent layer of spores ; (3) tho protoplasm 

 forms a parietal layer of variable thickness, but always less than tho 

 height of the subsequent layer of spores. Of these tho second caso is 

 the commonest. Immediate ly beforo the differentiation of the spores tho 

 appendage is formed, usually at tho apex of tho sporangium. In tho 

 earlier stages of the differentiation of tho spores, the entire parietal layer 

 of protoplasm forms itself into a network, consisting of polyhedral 

 portions of nearly uniform size. These aro separated by narrow, deep 

 vertical indentations, but arc not yet differentiated into spores. Where 

 the protoplasm occupies the whole of the sporangium, the latter is 

 entirely filled up by this network. After this condition has lasted for 

 a few minutes, the rudiments of the spores swell up so as to come into 

 close contact with one another, small vacuoles are formed, which rapidly 

 increaso in size and thon suddenly disappear, and the spores then become 

 rounded off and distinctly differentiated. Tho formation of the cilia was 

 distinctly observed, making their appearance as short hairs with slow 

 oscillating movement, and then growing rapidly in length, their oscilla- 

 tions increasing at the same time in rapidity. Tho spores now exhibit 

 a vibrating movement, which assumes a more lively character shortly 

 before their escape. About tho time that the cilia are being formed, a 

 very peculiar process takes place. At certain spots warts are formed on 

 the spores, which gradually elongate, and finally become separated as 

 lumps of protoplasm of variable sizes, often one-third the diameter of tho 

 spore. These move about for a time with a dancing motion, and then 

 become absorbed again into the same spore from which they sprang, 

 without apparently producing any change in it. If not again taken up, 

 others are formed in the same way; and this lasts for some minutes. 

 The spores escape in succession one after another, the first being ejected 

 with some violence. 



The process, as described above, is essentially the same also in other 

 species of Saprolegnia, in Aclilya polyandra and oblongata, Dictyuchus 

 clavatus and Leptomitus lacteus. Notwithstanding statements to the 

 contrary, the mode of formation of the sporangia in Aplianomyces is also 

 essentially the same as that in the other genera of the family. 



Herr Eothert also investigated the mode of formation of the oogonia, 

 and found it to agree in essential points with that of the sporangia, and 

 even in many small details. The formation of the parietal layer of pro- 

 toplasm, and of the network composed of the rudiments of " spores " 

 [oospheres], the mode of separation of the " spores," and other details, 

 are again repeated in the development of the oogonia. The ordinary 

 oogonia with few "spores" correspond to the sporangia with only a 

 parietal layer of protoplasm, the less common ones with many " spores " 

 to the normal sporangia entirely filled with protoplasm. 



Infection of a Frog-tadpole by Saprolegnia ferax.* — Prof. J. B. 

 Schnetzler had under observation two tadpoles ; towards the end of last 

 June, a fly (Sarcophaga carnaria) was placed with one of them. After 

 death the body of the fly became covered with filaments of Saprolegnia 



* Ann. and Mag. Nat. Hist., i. (1886) pp. 162-3 (Seance Soc. Valid. Sci. Nat., 

 July 6, 1887). 



