106 



Part III. — Twenty-seventh Annual Report 



On one part of the plate of Lot. I. there were 85 eggs on a surface half- 

 an-inch (12'5mm.) square. They were arranged in one layer. 



The eggs hatched after periods of incubation varying from 28 to 35 days, 

 in water of the temperature given in the following table : — 



Table giving the temperature of the water during the period of Incubation. 





I. 



n. 



III. 







I. 



II. 



III. 







r. 



II. 



III. 



Feb. 18 



*F. 



























„ 18 



4-4,5-6 







Mar. 



1 



3, 5 



3, 5 



3, 5 



Mar. 



13 



4-8 



4-8 



4-8 



„ 19 



0, 3-2 



F.3-6, 6 



F. 4 



> j 



2 



2-8, 4 



2-8, 4 



2-8, 4 



) > 



16 



4-4 



4-4 



4-4 



t > 20 



-1 -8, 0 



-1 -6,3-8 



-•4,5,6 



>> 



3 



4-5 



4-5 



4-5 



j j 



17 



4-2 



4 2 



4-2 



„ 21 



0, 6-8 



•4, 8-2 



6-8,8-7 





4 



4-9 



4-9 



4-9 



+ 



18 



4-2 



4 2 



4 2 



„ 22 



6-6 



6-6 



6-6 



> > 



5 



4-4 



44 



4 4 



? ? 



19 



^4-5 



/4-5 



/4-5 



t „ 25 



3-6,4-8 



3-6,4-8 



36,4-8 





7 



4 3 



4-3 



4-3 



j j 



20 



/5-3 



/5-3 



/5-3 



„ 26 



3-6,4-2 



3-6,4-2 

 3-2,4-6 



3-6,4-2 



>j 



8 



4-2 



4-2 



4-2 



>> 



21 



5 6 



5-6 



5-6 



„ 27 



3-2,4-6 



3-2,4-6 





9 



4-4 



4-4 



4-4 



>» 



22 



/6-7 



/6-7 



/6-7 



„ 28 



1-4,3-4 



1-4,3-4 



1-4,3-4 



>> 



10 



5-4 



5-4 



5-4 





23 



/8-3 



J 8-3 



/8-3 



„ 29 



2-2,2-8 



22,2-8 



2-2,2-8 



j j 



11 



5-7 



5 '7 



5-7 





25 



/5-6 



/5-6 



/5-6 











J 9 



12 



4-6 



4-6 



4-6 







*F. indicates the date of fertilization of the eggs, 

 t The temperatures on the following dates have been omitted :— Feb. 23 and 24 ; 

 Mar. 6, 14, 15, and 24. + Date upon which fry was obtained. /. Fry. 



Lots I., II., and III. in Cooled Water. — Ic. lie. IIIc. 



The majority of the eggs of Lots I., II., and III. were kept continuously in 

 cooled water. They are designated by the numbers Ic, lie, and IIIc 



Feb. 21. — The eggs of Ic. exhibited a solid blastodisc at this date (fig. 

 18). A very large quantity of little rod-like crystals were present inside 

 the zona on the yolk. These crystals (cr, fig. 26, etc.), were present in 

 large numbers inside the zona in the cooled eggs. 



Feb. 24. — The eggs of Ic. and IIIc. now showed a saucer-shaped cap 

 similar to the condition shown in fig. 3. The crystals were numerous 

 inside the zona in IIIc. The edge of the blastoderm extended to about the 

 middle of the yolk-sphere. lie. had the solid blastodisc shown in figs. 19 

 and 20. One egg which had a solid disc was left in a watch-glass over- 

 night in the Laboratory. Next morning the germ was in the thin saucer- 

 shaped condition (fig. 3). Some eggs showed a depression (de) in the yolk 

 under one side of the blastodisc (fig. 21). 



Feb 26. — The eggs of Ic. (fig. 22) were not very much advanced on the 

 stage found at the previous examination. The exterior of the egg was very 

 dirty. The sample of eggs of lie. showed various stages of the blastodisc 

 (cf. figs. 20, 23, 24, 2, 3) : one was seen in the stage of fig. 22. In IIIc. 

 the stages observed are shown in figs. 24, 25, and 26. There was a great 

 quantity of crystals present in the yolk and on the inside of the zona, and 

 especially at the edge of the blastoderm, where the latter appeared to be 

 pushing the crystals in front of it. The crystals (cr) are shown in fig. 26, 

 in which the blastopore seemed to be about to close. 



March 2. — Ic. and lie. were examined. The eggs are in the stage where 

 the blastopore (b.p.) is closed (fig. 27). There was a good number of dead 

 eggs. The plates occupying the last position in the cooled boxes, No. 1 and 

 No. 2, had no live eggs on them. The eggs, which were very dirty, had 

 been in the disc stage in the majority of cases at death, but some were 

 noticed in stages up to the closure of the blastopore. I consider that the 

 death of these eggs was due to insufficient aeration. A good many of the 

 eggs of IIIc. also were dead. The live eggs were in the stage shown in 

 fig. 28. The blastopore was closed, but I could not make out a free end to 

 the tail. 



