2 28 BYRNES. [Vol. XVI. 



There is no evidence of an " archoplasm " which is distinct 

 from the cytoplasm of the egg in Limax. 



There is no middle-piece to the spermatozoon. The asters of 

 the segmentation spindle very rarely appear before the apposi- 

 tion of the egg-nucleus and the sperm-nucleus. Sometimes, 

 though very exceptionally, they appear before the maturation 

 stages of the Qgg are completed. The sperm-asters cannot 

 be traced directly to the spermatozoon, although they are more 

 closely connected with the sperm than with the egg-nucleus. 

 The nuclei do not unite to form a segmentation nucleus. 



The spindle in Limax is not formed wholly by a rearrange- 

 ment of nuclear substance. 



While the old astral rays still persist around the centro- 

 sphere of the first maturation spindle, the second maturation 

 spindle is formed within the centrosphere. The polar rays 

 of the second maturation spindle project through the centro- 

 sphere out into the cytoplasm ; they are not formed by the 

 focussing about new centers of rays that are already formed. 



The asters of the second maturation spindle are newly formed 

 structures. The mantle fibers of the second maturation spindle 

 seem to be derived secondarily from polar fibers. The forma- 

 tion of the spiral aster in Limax agrestis occurs soon after the 

 extrusion of the second polar globule, and only then. When 

 seen from the upper pole of the egg the rays of the spiral aster 

 are bent in the direction of the movement of the hands of a 

 clock. 



The spiral aster is derived secondarily from an aster whose 

 rays are at first straight. Normally, the spiral arrangement of 

 the astral rays occurs in connection with the egg-aster. It 

 may, however, occur in connection with the sperm-aster under 

 special conditions. 



VIIL Appendix. 



Material : Collecting and Keeping. 



Limax agrestis, Linne, is a species of Limax common in 

 Europe. It has been introduced into this country and has 

 become very abundant in the neighborhood of Philadelphia. 



