418 BULLETIN OF THE 



this solution a complete separation ensues between the nuclear essence, 

 which goes to form the equatorial zone, and the nuclear fluid {sue), 

 which is repelled to the poles of the nucleus. After the division of the 

 zone into two nuclear disks which are to become the new nuclei, this 

 nuclear fluid loses itself in the body of the cell. The vacuoles of the 

 nucleoli are only the result of the momentary union of certain parts of 

 the nuclear substance with the nuclear fluid. 



In the case of the nucleus of the central cell of Dicyema, the use of 

 osmic acid followed by picrocarminate results in giving the nuclear sub- 

 stance a rose color, the nucleolus and membrane a bright red, and in 

 leaving the reticular substance unstained. 



In the disappearance of the germinative vesicle of Asteracanthion, 

 which takes place in exactly the same manner whether the eggs are 

 fertilized or not, the nucleoplasm and pseudo-nucleoli first disappear, 

 then the dot and the contour of the vesicle become paler, the vacuoles 

 of the dot become confluent, and the surface of the dot gradually be- 

 comes lobed and finally breaks up into a large number of fragments 

 which separate and spread through the whole vesicle. These fragments 

 increase a little in volume, become less refractive, and finally cease to 

 be visible. Some seconds after this the membrane of the vesicle be- 

 comes ruptured on the side toward the centre of the egg and parts of 

 its contents escape ; the membrane finally dissolves away, and there 

 remains only a clear spot, with ill-defined and increasingly irregular con- 

 tour. The spot diminishes in size till it vanishes. Van Beneden saw 

 the polar globules * " formed under his own eyes," but is unable to give 

 any account of their real origin. All his observations appear to have 

 been made on living eggs, which accounts for his having overlooked 

 many facts. 



The principal conclusions of Van Bambeke (76, pp. 99-117), reached 

 by the study of Pelobates, Triton, and Axolotl, have already (p. 389) 

 been stated. It only remains to add that he never observed the for- 

 mation of polar globules, but in eggs of the Axolotl, immersed in 

 alcohol immediately after fecundation, he discovered the existence of 

 a whitish spot at the niveau of, and all around, the fovea germinativa, 

 caused by a superficial layer of probably coagulated albuminoid matter, 

 which gradually thinned out toward its periphery. This layer presents 

 in section (PI. II. Figs. 5 and 6) a striation perpendicular to its sur- 



* By a double error of translation " corps directeurs (globules polaires) " appears 

 in the English translation in the absurd form of "distinctive bodies and polar glob^ 

 ules." 



