464 BOTANICAL GAZETTE [December 



The similarity of the habit of this creeping expansion of the 

 thallus to that of Aglaozonia in nature is striking. The material of 

 Aglaozonia collected fresh from Posilipo and Nisida, which has 

 grown creeping on a sea-urchin's shell or on the rock, showed a 

 number of forms in various stage of development. If the creeping 

 expansion of the thallus obtained in cultures is compared with 

 Aglaozonia of similar size as it occurs in nature, it is hard to find 

 any difference in their appearance. Not only the zonal growth and 

 occasional intercalary growth of the thallus is alike in these two 

 forms, but also the cell structure as seen in sections under the micro- 

 scope is remarkably similar in the two forms. The nuclei of the 

 thallus obtained in culture contains 48 chromosomes, and the same 

 number is present in Aglaozonia as it occurs in nature. 



The author's cultures of the thallus expansion, the Aglaozonia 

 form of Cutleria, were not continued up to the stage of producing 

 reproductive organs. 



GERMINATION OF THE UNFERTILIZED FEMALE GAMETES 



As was described before, the female gametes after their escape 

 from the gametangia may swim for as long a time as 2 hours, or 

 for as short a time as 5 minutes. When the motion becomes slug- 

 gish, the body becomes spherical, the plastids which have hitherto 

 occupied the more posterior portion of the body become irregularly 

 scattered throughout, and finally the cilia are either withdrawn 

 or they coalesce with the plasma membrane as the movement ceases. 

 If the female gametes in this condition are kept with no addition 

 of the male gametes, they remain dormant for a considerable time. 

 The female gamete left in this condition at length shows a change 

 in the outermost layer of the plasma membrane that is in direct 

 contact with sea water, the change resulting in the development of a 

 cell wall, thin at first, and then increasing in thickness. The 

 nucleus is in the resting condition (fig. 124). Not infrequently 

 it is observed that the female gamete, now inclosed within a cell 

 wall, has an elongation at a part of the body where the cell wall is 



thickened (figs. 125 



- 7 —V w 



female gamete commences to divide 24-28 



hours after it has assumed 



mitosis 



