DKVELOPMENT OF THE OSTRICH FERX. O.-t 



The neck-cells of the ripe archegoniuin possess the same property of absorbing large 

 quantities of water that was observed in the parietal cells of the antheridium; and be- 

 coming much swollen the pressure exerted upon the contents of the canal is sufficient to 

 force apart the upper neck-cells, which finally divei-ge widely, allowing the contents of 

 the canal to escape, leaving a clear passage down to the germ-cell (PI. 5, fig. 7). This 

 process can be easily seen by allowing prothallia upon which there are mature archego- 

 nia to remain somewhat di-y for two or three days. Longitudinal sections of these be- 

 ing made and mounted in water Avill be certain to show some arehegonia ready to open, 

 and generally within a few minutes sufficient water will have been absorbed to force 

 open the neck and discharge its contents. For a satisfiictoi-y study of the development 

 of the archegonium, these longitudinal sections of the prothallium are necessary, arehe- 

 gonia in all stages of development being found in the older prothallia. 



The upper cells of the archegonium separate slowly at first, this being accompanied 

 by a slight discharge of mucilage. As water continues to be absorbed by the neck-cells, 

 they become much swollen and the upper cells are toi'u apart, often with violence enough 

 to detach entirely some of the uppermost ones. At the same time, by the inward press- 

 ure, the remaining masses of mucilage are forced out, collecting in masses of some size 

 around the opening of the archegonium (PI. .5, fig. 7). Besides the granular masses 

 which are mainly composed of the protoplasm of the neck-cell, there is a quantity of vis- 

 cid, perfectly colorless and transparent matter, whose presence is made evident by the 

 behavior of the antherozoids that come in contact with it. The antherozoids collect in 

 greater or less numbei's about the month of the open archegonium, their movements be- 

 ing retarded by the mucilaginous matter expelled from the nock, but by far the greater 

 number are not detained by the mucilage, or only temporaril}^; and of those held, only 

 a very small jjart ever enter the archegonium. When an antherozoid comes within the 

 immediate vicinity of tlie archegoniiun, its movements are very much checked, there be- 

 ing evidently some substance present that interferes with the free movements of the cilia. 

 One may frequently be seen to come to a sudden stop, and after vigoi'ous efforts to free 

 itself, swim away with undiminished vigor. The canal of the archegonium appears to 

 be filled with the same substance, for although nothing is visible the movements of the 

 antherozoids are so much checked that in nearly every case oliserved, they failed to 

 penetrate to the germ-cell, although making their way foi* some distance down the 

 neck. This necessitates the finlilization of the germ-cell by a fresh and active anthero- 

 zoid, as only such would have strength to make its way down to the germ-cell. 



The entrance of the antherozoid into the neck of the archegonium was observed a 

 number of times, and in one case one was detected within the central cell. Before en- 

 tering the movements cease almost entirely for a few moments, and are then resumed, 

 the body being somewhat stretched and the movement slowly rotary; at the same time, 

 by a quick movement of the pointed end of the body, the vesicle is thrown off" (PI. 5, 

 fig. 9). 



In the single case in which the antherozoid was observed Avithin the central cell, the 

 form of the antherozoid could not be clearly made out, though the movement of the cilia 

 was plainly seen for several minutes, when it ceased, and the antherozoid became lost to 

 view, presumably fusing witli the germ-cell, but its mode of entrance could not be made 



MEMDIKS noSTON 8(>C. NAT. IIIS!'., VOI>. !\ . 1 



