INTRODUCTION 



13 



of the plasraodium continued to creep over the Auricularia 

 for several days after these observations had been made. 



This experiment affords clear evidence that under certain 

 conditions the nuclei of the actively streaming plasmodium 

 divide by karyokinesis, but what these conditions are remains 

 at present unexplained. The process no doubt is a rapid one, 

 occupying about half an hour ; but the following observations 

 point to the conclusion arrived at from many previous experi- 

 ments, that it is not the only way by which the nuclei increase 

 in number. A rapidly increasing plasmodium of Badhamia 

 spread over two pilei of Auricularia in the course of fourteen 

 hours ; during this period a portion of the plasmodium was 

 taken every quarter of an hour, and smeared on a coverslip 

 and stained. Each of the fifty-five mountings shows the 

 nuclei in the usual vast abundance, suggesting that their 

 numbers had increased, pari 

 passu, with the growth of the 

 plasmodium, and in none of 

 them is there any appearance 

 of karyokinetic division. From 

 the time occupied by the 

 karyokinetic process in the 

 maturing sporangium we are 

 satisfied that it could not have 

 escaped detection if it had 

 occurred during those fourteen 

 hours (fig. 6). It would therefore 

 appear probable that a multi- 

 plication of nuclei had taken 

 place by some other means. 





\*l 





Fig. 6. — Badiiamia. utricularis Berk. 

 Group of nuclei from actively feeding 



They Vary in Size from 2* 5 to 5 yu.. plasraodium that covered two pilei of 



fWfl<?irmflllv thpr^ arp nnwnr Auricidaria in fourteen hours, showing the 

 wcuctbiunctny wieie die d.pped,i- ^regular size of the nuclei and large nucleoli. 



anceS which Strongly Suggest . Stained in picro-carmrae and mounted 

 j . . . -, , . . . ° J . °* in Canada Balsam. Magnified 1200 times. 



that simple division of a nucleus 

 is taking place. Some days later 



when the plasmodium had ceased to feed, and was collecting 

 together to form into sporangia, stainings showed the nuclei 

 more equal in size, measuring 4 to 5 p in diameter. This 

 experiment may be taken to add materially to the evidence 

 that under some conditions the increase in the number of the 

 nuclei is brought about by simple division.* 



The plasmodium of the exosporous Ceratiomyxa issues from 

 the interior of rotten wood to form cushion-like heaps which 

 rapidly extend into columnar or branching sporophores. As 



* I learn by correspondence with Dr. Jahn that in preparations of creeping Plas- 

 modium made at successive intervaLs he has again obtained the mitotic division of the 

 nuclei. I)r. Jahn inclines to the view that the increase of nuclei in the Plasmodium 

 occurs solely by this process, but as stated in the text, it is desirable that further in- 

 vestigation as to the mode of increase should be made. — G. L. 



