FURTHER STUDIES ON THE PRODUCTION OF FUNC- 

 TIONAL AND RUDIMENTARY SPERMATOZOA IN 



ROTIFERS. 1 



D. D. WHITNEY. 



In a recent paper some general observations were recorded in 

 regard to the dimorphic spermatozoa found in the parthenogenet- 

 ically developed males of nine species of rotifers. Some of the 

 stages in the development of the spermatozoa from the cells of 

 the last spermatocyte-divisions in Brachionus mulleri were de- 

 scribed and figured. No studies, however, were made on the 

 nuclear material of the spermatozoa either to determine whether 

 it was present in both kinds of spermatozoa or to determine in 

 what part of the spermatozoa it was located. 



Additional studies now have been completed in an attempt to 

 observe these points. These studies have been made in consid- 

 erable detail on the marine species, Brachionus mulleri, and in 

 lesser detail on Hydatina senta, Brachionus amphiceros and 

 Diaschiza sterea. As the earlier paper had some of the details 

 of the formation of the spermatozoa of Brachionus mulleri and 

 as this rotifer is one of the most convenient forms to maintain in 

 the laboratory and also a very convenient one from which to 

 obtain immature males the majority of the observations were 

 made on material from this species. 



Several killing and fixing fluids and stains were tried but 

 Zenker's fluid followed by Delafield's hematoxylin proved to be 

 the most satisfactory method for making clear mounts of the 

 entire cells. The living males were crushed under a cover glass 

 in culture water and favorable cells were selected under the 

 microscope. The killing fluid was allowed to run under the 

 cover glass and to remain from 10-20 minutes. Later the killing 

 fluid was drawn out by filter paper and distilled water allowed 

 to take its place. After the distilled water had been changed 

 several times from under the cover glass Delafield's hematoxylin 



1 Studies from the Zoological Laboratory, The University of Nebraska, No. 119. 



325 



