Vol. XXXIII. November, 1917. No. 5. 



BIOLOGICAL BULLETIN 



THE PRODUCTION OF FUNCTIONAL AND RUDI- 

 MENTARY SPERMATOZOA IN ROTIFERS. 1 



D. D. WHITNEY. 



Marked dimorphism in the spermatozoa of a few animals has 

 been briefly recorded by several observers, but no detailed study 

 has been made of such forms to determine how the two kinds of 

 spermatozoa are formed nor has there been offered an explana- 

 tion as to their probable functions. While looking at the plates 

 in "The Rotifera," by Hudson and Goss, I noticed sketches of 

 the two dimorphic spermatozoa of the marine rotifer, Brachionus 

 miilleri. As this rotifer occurs in countless numbers in a salt- 

 water lake near Lincoln, Neb., an excellent opportunity was 

 offered to reexamine it in an attempt to find an explanation for 

 the production of the two kinds of spermatozoa. After reex- 

 amining the spermatozoa of this rotifer and confirming the 

 observations of Hudson and Goss the spermatozoa of eight other 

 species of rotifers were examined and were found also to be 

 composed of two kinds. Thus indicating that this phenomenon 

 of dimorphism of spermatozoa may be general for all the species 

 of the whole group of rotifers which produce male individuals. 



The technique of examining the spermatozoa is very simple. 

 Mature free swimming males were placed on a slide in a drop 

 of the culture water and covered with a cover glass. Then by 

 pressure the males were forced to eject the contents of the single 

 testis into the water. The two kinds of spermatozoa could be 

 readily seen even with the low powers of the microscope and were 

 as easily counted. Early stages in the development of the 

 spermatozoa as far back as the early spermatids were studied 

 by crushing the eggs containing the unhatched immature males. 

 All stages of development from the earliest spermatid up through 



1 Studies from the Zoological Laboratory, The University of Nebraska, No. 117. 



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