180 BALBIANI, ON SEXUAL 



to suppose that^ in making it, the eminent professor did not 

 himself consider it altogether correct. What, then, is the real 

 nature of this nucleus ? For ourselves, we see in it but an 

 egg Avith its constituent elements, namely, its granular yolk, 

 its germ-vesicle, and its germ-spot/' That such is the 

 corrrect interpretation, M. Balbiani further shows by an 

 appeal to the changes which the nucleus of Chilodon under- 

 goes, previous to. each reproductive epoch. Its entire con- 

 tents then group themselves " into one elementary cell, into 

 a germ which sums up in itself the whole plastic force of the 

 organ. And what is, perhaps, more singular still, this germ 

 shares the same changes as its possessor, divides, like it, at 

 each spontaneous fission, and transmits itself to the successive 

 generations which result from this mode of propagation, to 

 an extent almost unlimited.^' 



The Nucleolus or Testis. 



Of somewhat similar structure, the nucleolus or testis 

 is always much smaller than the ovary to the surface 

 of which it adheres. " Often the two corpuscles, male and 

 female, are merely in contact by their outer membranes; 

 but, in other cases, not less numerous, the first is received 

 into a more or less deep depression on the surface of the 

 second, within which it sometimes seems wholly to disappear. 

 Each, nevertheless, preserves its owti envelope. The blend- 

 ing together of these two bodies is frequently so complete 

 that, in order to discover the concealed position of the male 

 corpuscle, it is necessary to make use of reagents which, 

 like dilute acetic acid, determine the condensation of their 

 substance, and bring their walls into view. A tiny clear circle 

 then becomes formed around the nucleolus, which isolates it 

 from the mass of the ovary, and serves to render it visible. 

 But, in many cases, whatever be the means employed, we 

 cannot prove that it exists ; hence we may conclude that it 

 is reduced to nothing in the intervals of the reproductive 

 periods. It is not rare, in fact, to see it make its appearance 

 at these epochs, in individuals in which its presence had 

 been vainly sought until then. Another very serious diffi- 

 culty accompanying the discovery of this organ results from 

 its close resemblance at times to the fatty globules so abun- 

 dant in the bodies of all Infusoria, almost every optical cha- 

 racter of which it shares. It has the same smooth and 

 rounded form, the same homogeneity, the same refractive 

 aspect, especially after treatment by acids which determine 

 the contraction of its substance. Much experience, there- 



