BULLETIN OF THE UXITED STATES FISH COMMISSION. 181 



just beginning to bud out as a rounded knob, as in 24 to 36-liour embryos 

 liatclied in water ranging from 80° to 72° F. 



" Eggs of June 7, partially developed, have commenced to collapse in 

 the refrigerator box. This appears to be due to the growth of the fungus 

 on the ova. 



" June 13, 10 a. m. — Examined the eggs put into the refrigerator on the 

 night of the 8th. They are now nearly all dead. Those not affected 

 with fungus mycelium still plump, and normal in development ; caudal 

 knob, but a little more prominent than when examined on the 12th, at 

 11 a. m. Temperature in box, 53° F." 



We may sum up the result of these experiments as follows : 



After a little more than four and a half days the ova of the shad exposed 

 on cloth trays to a temperature of about 52° F. have not advanced farther 

 than they would have done in water at a temperature o/80° F. in 24 hours, 

 or in 30 to 36 hours in water at a temperature of 74° to 68° F. 



But after four and a half days our embryos have not yet passed through 

 half of their development, so that it would be safe to say that the period 

 of incubation at this rate could be prolonged for nine days, or a period 

 long enough to readily admit of the transportation of ova, so retarded, 

 across the Atlantic to England, France, or Germany. The bar to our 

 comi^lete success, however, was the rapid and fatal development of the 

 fungus, which is jirobably a saprolegnious form identical with the one 

 commonly j^roductive of more or less loss in hatching out ova in water 

 in all the forms of apparatus which I have seen used. If attention were 

 directed to a means of destroying the germs of these organisms I think 

 success might be very confidently anticipated. To effect the comj»lete 

 destruction of the spores in the water used, and to prevent their ever 

 coming into contact with the eggs upon which they lodge, germinate, and 

 grow, are the preventive measures to be adopted. These measures are, 

 I believe, feasible, but may involve some trouble in their execution. The 

 experiments of Tyndall and Pasteur have taught us that it is possible to 

 sterilize any fluid and render it absolutely free from all forms of organic 

 germs by energetic boiling, taking care afterwards to exclude the germ- 

 laden air by means of stopj)ers of cotton wool, or by hermetically sealing 

 the vessel. Such a method would, of course, not answer in this case, as 

 in sealing up a vessel containing the eggs in sterilized water they would 

 be smothered. The precautions which are practicable, however, are 

 these : (1) Take care to scald and thoroughly sterilize the pans into which 

 the fish are spawned ; (2) take care to wipe the spawning fish clean, and, 

 above all, avoid rubbing off the scales or to allow these to drop into the 

 spawn or milt ; (3) use only sterilized water to " bring up" or water-swell 

 the eggs; (4) take care to scald out the refrigerator and cloth trays, so 

 as to sterilize these of any germs; (5) it would also be necessary to boil 

 and sterilize enough water to keep the eggs and cloth trays moist during 

 the process of retardation; (0) the sterilized water should be kept tightly 

 covered in a clean vessel ; (7) in managing the refrigerator care should 



