Volume II JUNE, 1903 No. 3 



ACTINOSPHAERIUM EICHORNI. 



A BIOMETRICAL STUDY IN TUE MASS RELATIONS OF 



NUCLEUS AND CYTOPLASM*. I IRRARY 



mEW YORK 



By GEOFFREY SMITH, New College, Oxford. 



Introduction. 



The followiiig study is concerned with what appears at present to be the 

 critical problem of cytology, the inter-relation of micleus and cytoplasm, or more 

 strictly of chromatiu aud cytopla.sni. M\ich knowledge of chemico-physiological 

 significance is possessed by naturalists oii this head, bat concerning the mass 

 relatioiis that hold between chromatin and cytoplasm nnder different physiological 

 conditions, a knowledge of which one would consider fundamental from a chemico- 

 physiological point of view, stiangely little is known. How important this mass 

 relation may lie is brought home to one who remembers that tlie most obvious 

 distinction between the male and female sexual cells throughout organic nature is 

 this very one of the mass relations between chromatiu and cytoplasm. 



In Order that the following observations and e.xperiments on Actin osphaerium 

 may be easily grasped, I will shortly recapitulate the history of its encystment 

 and reproduction. 



Encystment may be induced by starvation for a longer or shorter period. 

 The creature about to encyst becomes much vacuolated, and fixes itself to the 

 vessel in which it is confined, withdrawing its pseudopudia. The endoplasm 

 becomes exceedingly opaque, appearing conspicuously white to the naked eye, 

 and shortly afterwards it breaks up into a varying number of discoid bodies lying 

 in the gelatinous exoplasm, each of which contaiiis a single nucleus. During the 

 course of the next twenty-four hours each mother cyst divides to form two 

 daughter cysts ; the nucleus of each daughter cyst novv divides twice, giviug off 



* By the permission of the authorities of New College, Oxford, I was enabled to woik in Professor 

 E. Hertwi(,''s laboratory at Munich durin;» part of the winter of 11102. Throuph his attention and 

 guidance it has been possible to bring this research to some result. 



Biometrika ii 3X 



