4 



394 BULLETIN OF THE 



and sharp membranous limitation from the yolk, which it hitherto pos- 

 sessed, and becomes an elongated body. Its coherence and elasticity 

 make it possible by gentle pressure to remove it from the yolk without 

 changing its form or size. In regard to its composition, it presents a 

 peculiar appearance. Its middle portion is, in comparison with its poles, 

 swollen, and exhibits a meridional striation, which results from the pres- 

 ence of a membranous envelope. Inasmuch as the remaining [polar] 

 portions of this modified germinative vesicle present no trace of a mem- 

 brane, and inasmuch as the median swollen portion agrees very well in 

 size with the [unaltered] germinative vesicle, the whole structure may 

 be considered as having arisen by the accumulation of protoplasm at 

 two opposite poles of the vesicle. The germinative spot had already 

 disappeared. 



The expression " meridionale Streifung " might lead one to suppose 

 that an equivalent of the spindle fibres had been observed, were it not 

 that the '' Streifung " shown in the figure (Fig. 5) "has a direction at 

 right angles to the axis of the supposed spindle figure. Although no 

 stellar structures are indicated, I think one must conclude that the 

 figure represents an early stage in the formation of the amphiaster, 

 whose rays may easily have escaped detection. Whether the centres of 

 the hypothetical asters are to be imagined as occupying the centre of the 

 clear areas, or whether they correspond to the extreme points of the 

 figure, cannot be definitely concluded. That the astral centres muT/ lie 

 at considerable distance from the periphery of the nucleus, has been 

 sufficiently insisted upon already in the detailed account of Limax. 

 The folding of the membrane, to which is due the striate appearance, 

 entirely precludes the interpretation of the central mass as an oblique 

 view of the nuclear disk. Polar globules are not mentioned. 



Afterwards Ratzel {'69'', p. 282) endeavors to correct the observa- 

 tions made by himself and Warschawsky on Lumbricus, as far as 

 regards the disappearance of the germinative vesicle, which he now 

 maintains gives rise by its division to a number of clear spots. 



As I have briefly stated before, Oellacher (72 and 72^ pp. 406-410) 

 has described the process by which the germinative vesicle is eliminated 

 from the q^^ in the case of the trout, and also in that of the hen. (See 

 also Oellacher 70.) By the contractions of the protoplasm of the germ, 

 the vesicle is forced to the free surface, w^here it becomes ruptured, and, 

 in the case of the trout, its thick wall is spread out on the surface of 

 the germ as a flat, round veil. The contents of the vesicle thus set 

 free appear in the form of one or two finely granular spherules on the 



