180 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



keel or carina lias been developed. Temx)eratnre 53° F. in refrigerator 

 all day. Eggs in a cone of the same age, temperature of the water 65° 

 F., have the embryos well advanced, with the tail free and as long as 

 the i)ortiou of the body still in contact with the yelk, but the natatory 

 fold is not developed. 



" Eggs which had progressed a considerable way in development, so 

 that the tail was somewhat more advanced than the stage last described, 

 and which did not yet have the eyes pigmented, were also experimented 

 upon at this time. In consequence, it was learned that such might be 

 suddenly transferred from the water in which they had previously been 

 undergoing development to the damp cotton-cloth trays without injury 

 from such sudden and continued exposure to an air temperature of 53° 

 F. A most striking fact was that in such as had the choroid or pig- 

 mented coat of the eyes in process of development had the formation of 

 the pigment arrested in correspondence with the general arrest of de- 

 velopment observed. 



" Eeturning to the eggs of the 8th June : These were examined June 

 11, 9 a. m. Development is still normal ; the eyes are perfecting, but 

 the perfectly normal blastoderm does not yet quite cover the vitellus, 

 the diameter of the opening; at the caudal pole, where the vitellus or 

 yelk is still exposed, being equal to about one-seventh of the circumfer- 

 ence of the egg. Temperature during the night, 49.5° F. 



"Other lots of ova, taken on the Gth and 7th June, and removed from 

 the hatching-cones and put on the cloth trays in the refrigerator box, have 

 been greatly retarded, but the development is normal, no abnormali- 

 ties whatever having been observed. The lot, taken on the 8th and put 

 into the refrigerator on the 9th, after having been in the water for 24 

 hours, are well advanced, the tail being twice as long as the portion of 

 the embryo's body attached to the yelk, and the fin-folds are nearly fully 

 developed, dorsally and ventrally. 



" The eggs first put into the refrigerator on the evening of the 8th 

 June now show a disposition to wrinkle, i. e., part with the water 

 inclosed between the egg-membrane and tlie vitellus, and are collapsing. 

 Perhaps this is due to evaporation." Afterwards I abandoned the view 

 that evaporation was the cause of the collapse and wrinkling of the egg- 

 membranes. I am now fully convinced that it was due to the invasions 

 of a fungus. 



"Same lot of eggs of June 8 examined June 11, at 7 p. m. Blasto- 

 derm not yet quite, but very nearly, closed over the vitellus. Only a 

 very small round opening at the tail of the embryo marks^ the point 

 where its closure is about to take i)lace. Temperature, 53° F. in refrig- 

 erator. Development normal in those which are not collapsing, after 

 remaining 70 hours on the trays. 



"June 12, 11 a. m. — Eggs of June 8 in refrigerator for the most part 

 still alive. Temperature, 52° F. Development has been normal up to 

 this point; the blastoderm has closed over the vitellus, and the tail is 



