Biqelow. — Nuclear Cycle of Gonionemus luurbaclrii. 



EXPLANATION OF PLATES. 



All drawings were made with the aid of a camera lucida. All the figures are 

 reproduced without reduction. In the description of each figure the magnification 

 is given. 



The magnification of 2600 diameters was obtained with a Bausch and Lomb 

 ^ inch homog. immersion objective and i inch eyepiece at a projection distance of 

 450 mm.; that of 1780, witli ^j objective and 1 inch eyepiece, projection distance 

 450 mm. ; that of 900, with j^ objective and 2 inch eyepiece, projection distance 

 350 mm. ; and that of 500, with a D objective of Zeiss, 1 inch B. & L. eyepiece, pro- 

 jection distance 350 mm. 



ABBREVIATIONS. 



ec'drm Ectodermic covering cells of gonad. 



en'drm Endoderm of radial canal. 



ms'gl Mesogloea. 



o'cjj. 1 Pseudoprophase of oocyte. 



o'cy. 2 Growth stage of oocyte. 



o'go Oogonium. 



sp'cy. 1 Primary spermatocyte. 



sp'cy. 2 Secondary spermatocyte. 



sp'd Spermatid. 



sp'go Spermatogonium. 



sp'zo Spermatozoa. 



