[5] RETARDING DEVELOPMENT OF SHAD EGGS. 79^ 



" 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 further 

 than they loould hare done in trafer at a temj)eratnre ofS(P F. in 24: hoursy 

 or in 30 to 36 hours in water at a temperature of 71° 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 j)rolougetl ior nine days, or a jjeriod 

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

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

 complete success, however, was the rapid and fatal development of the 

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

 commonly productive 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 complete 

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

 coming into contact with the eggs,up6n 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 stoppers of cotton wool, or by hermetically seal- 

 ing 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 ])rocess of retardation ; (G) the sterilized 

 water should be kept tightly covered in a clean vessel ; (7) in managing 

 the refrigerator care should be taken in opening and closing it, and in 

 order to ventilate it the opening in the upper part of the chamber for 

 the admission of air should be provided with a filter of cotton- wool ; (8) 

 it would be necessary to scald and sterilize new cotton cloths, since 

 these are almost always laden with germs. These precautions observed. 



