BULLETIN OF THE UNITED STATES FISH COMMISSION. 18$ 



work. Ill the glass vessels the estimate is very nearly accurate and 

 very easily made. 



In hatching white perch or other adhesive eggs, if the strings with 

 ova adhering to them were hung into the McDonald jar, into which a 

 quantity of shad ova had also been introduced, I think it altogether 

 probable that the attrition of the shad eggs against the perch eggs 

 would prevent the latter from becoming infested. The shad ova in their 

 rolling movements over the others would tend to prevent the lodgment 

 of fungus spores, as already pointed out in my discussion of shad ova. 



In the English edition of Maout and Decaisne's Botany, p. 975, I find 

 the following account of the egg fungus or alga as it is indifferently 

 called by different authorities. In order to disseminate a fuller knowl- 

 edge of its life history I will here reproduce what these distinguished 

 writers say of it : 



" These singular vegetables are considered to be fungi by some botanists ; 

 they live, in fact, on organic matters in a state of decomposition in 

 water, where they act upon oxide of iron by decomposing the carbonic 

 acid, absorbing the oxygen, and thus setting free the sulphuretted hy- 

 drogen, which destroys the vegetables or animals near it. [This indi- 

 cates the great importance of at once removing from the hatching ves- 

 sels any masses of fish ova which have become infested.] Notwith- 

 standing the significance of these biological phenomena, several phy- 

 siologists who have carefully studied Baprolegniecc do not hesitate to 

 class them amongst Algae. ' Saprolegnia feraxf says Thuret, ' is usu- 

 ally found on the bodies of drowned animals, which it covers with a 

 whitish down ; it even attacks live fish. Nothing is easier than to pro- 

 cure this singular Alga. Let a vase be filled with water from a garden 

 tub, and some flies be thrown into it, and it will usually be developed 

 in a few days. The body of the fly becomes covered with hyaline fila- 

 ments, which radiate around it, enveloping it with a whitish zone. Un- 

 der a miscroscope, these filaments are seen to be continuous, simple, or 

 scarcely branched, and to contain minute granules, which show a mo- 

 tion resembling that which is seen in the hairs of Phoeuogams. These 

 granules are very numerous, especially towards the upper extremity of 

 the tube, to which they give a gray, somewhat russet tint. This portion 

 soon becomes isolated from the rest of the filament by the formation of 

 a diaphragm. Then the contained matter coagulates in small masses, 

 which become more and more sharply defined, and end by forming so 

 many zoospores. These phenomena succeed each other very rapidly ; 

 often in less than an hour the granular matter becomes condensed at 

 the top of the filament, the septum forms, and the zoospores appear. 

 Finally the tube, which has a small protuberance at its extremity, 

 bursts there, and the zoospores escape, the first with impetuosity, the 

 others more slowly ; they are turbinate in shape, and furnished with 

 two hairs. This is not the only mode of reproduction possessed by 

 Saprolegnia ; another phenomenon succeeds. The filaments emit small 



