176 REPORT—1905. 
than in the others ; this substance must accordingly be removed from this 
class and placed in the next. 
2, Degeneration and death occur much earlier in lithium bromide, 
potassium bromide, sodium iodide and ammonium sulphate than in the 
remainder. In these four salts the medullary groove never closes, even if 
it is formed ; the auditory vesicles, infundibulum, optic vesicles, ccelom, 
heart and suckers are never developed. It would be better, therefore, to 
put this group by itself as a second class. 
(3) To the remainder potassium sulphate must now be added. 
In all these salts a considerable degree of differentiation takes place, 
but the embryo is unable to elongate. The blastopore is often closed, as 
also are the medullary folds. Optic vesicles, auditory vesicles and 
infundibulum are formed, often a small peritoneal cavity, and sometimes 
(lithium nitrate) a pericardium and heart, or a trace of the pronephros 
(potassium chloride). These embryos always die without hatching out ; 
the innermost layer of the jelly does not expand and leave the embryo 
room to elongate, as happens in normal development at about the time 
when the medullary folds are formed. i 
C. In the third class of the last report were placed those solutions— 
sodium chloride and nitrate, magnesium chloride, nitrate and sulphate, 
cane sugar and dextrose—in which, though this elongation takes place, 
development is nevertheless distorted and death eventually ensues. 
As noted above, it has now been found necessary to associate the 
bromide with the nitrate and the chloride of sodium in this class ; further, 
it is advisable to make a distinction between (1) these three sodium 
salts, (2) the three magnesium salts, and (3) the two sugars. 
(1) In the bromide, chloride, and nitrate of sodium the blastopore as 
a rule does not close and the medullary folds remain open, usually only in 
the region of the brain, though sometimes throughout. The variability 
exhibited by eggs of the same batch in the same solution in this respect 
is very remarkable. 
A tail is formed—sometimes single, sometimes double ; and gills 
(external) and gill-slits, blood-vessels, pronephros, and glomus are present. 
The embryo may even hatch out and attach itself to the jelly by its 
suckers, but it soon falls to the bottom and dies. 
2) The three salts of magnesium are more favourable to development. 
The blastopore closes, and a fairly long tail, provided with a fin, grows 
out ; but the brain remains open and undergoes the same grey degenera- 
tion, as described in the previous report, found in the monsters produced 
in the solutions already mentioned. 
Such internal organs as the eyes, the heart and pericardium, the 
blood-vessels, the pronephros, and duct are better developed than before. 
(3) The solutions of dextrose and cane sugar stand apart from the rest. 
The blastopore closes, though slowly, and the yolk-plug is withdrawn 
in both, 
In dextrose the medullary folds nearly close without undergoing any 
marked degeneration, and the embryo differs mainly from a normal one 
in the great retardation of development ; the optic vesicle, for example, 
appears five days later in the dextrose embryo than in the controls. 
In cane sugar, on the other hand, the medullary folds remain widely 
open and suffer grey degeneration ; and the embryo dies before the heart, 
the blood-vessels, the optic cup and lens, the gill-slits and the pronephros 
are formed. 
