452 BULLETIN OF THE 



nected with the fecundation ; and finally, that in the archisperms an 

 equivalent of the " Bauchkanalzelle " is formed, and that perhaps the 

 separation of the contents of a " vegetative cell " in the pollen grains of 

 archisperms has a preparatory significance for the formation of fecundat- 

 ing substance. But a difficulty in the way of this view for the spermato- 

 zoids of archisperms is the fact that in Selaginella and other Dichotomeae 

 both the " vegetative cell " and the " vesicle " are present. 



Before the maturity of the egg of Asteracanthion, there is, says 

 0. Hertwig ('78), a migration of the germinative vesicle toward the 

 surface of the yolk, where it loses its intra-nuclear network, and where 

 its membrane becomes uneven by reason of infoldings. He recognizes 

 that the germinative dot is composed of two substances, which differ 

 both in the fresh condition and more emphatically when treated with 

 reagents. The smaller portion lies as a protuberance on the larger, or 

 may be entirely surrounded by the latter ; it is more promptly and 

 deeply stained, and resists the swelling influence of ammoniacal fluids 

 longer, than the larger portion ; the latter becomes in 2-4% acetic acid 

 quite transparent, while the former becomes intensely lustrous. 



The changes at the time of maturation are inaugurated in the proto- 

 plasm which surrounds the vesicle. In the living eg^ it is seen that a 

 knob (Hocker) of protoplasm pushes its way into the germinative vesicle 

 from the side which lies nearest the surface of the yolk. The apex of 

 the knob embraces a light spot free from yolk granules, and sends out 

 long protoplasmic projections in all directions. The nucleolus now 

 (fifteen to twenty minutes after the eggs are brought from the ovary 

 into sea-water) loses its several vacuoles and thus appears homogeneous ; 

 in a short time there arises in its centre a larger single vacuole, that 

 is nearly filled by a solid round body, which by the use of reagents is 

 shown to be the same as the above-described smaller portion of the nu- 

 cleolus. Suddenly this vacuole with its contained corpuscle disappears. 

 What becomes of the corpuscle is shown only by employing reagents. 

 The observed stages probably follow each other in this order : the 

 corpuscle lying in the vacuole elongates, becomes pear-shaped, then 

 club-shaped, at length more rodlike, and finally a series of beadlike en- 

 largements. It has thus come to project with its smaller end through 

 the rind of nucleolar substance surrounding the vacuole, and its extrem- 

 ity is at last found to extend into the protoplasmic knob and to occupy 

 the centre of its stellate figure.. This is accomplished in the course of 

 about ten minutes. Then there appear in the centre of the stellate 

 figure granules which consist of nuclear substance and are probably de- 



