1884.] 51 [Hyatt. 



duce active fertilizing elements, or spermatozoa; while the fe- 

 males, like eggs in the higher animals, remain less differentiated, 

 or arrested in development and larger in size, and await contact 

 with the male before becoming strong enough for reproduction by 

 division. As Btitschli states it, " nicht nur die mannliche Gamete, 

 sondern auch die weibliche durch eine Reihe fortgesetzer Theilun- 

 gen aus einer gewohnlichen Zelle hervorgeht. Nur zeigt sich 

 hierbei die Tendenz, die Zahl der Theilungen, welche zu den 

 weiblichen Gameten ftihren, zu verringern, so dass diese letztern 

 allmahlich eine betrachtlichere Grosse darbieten, wie die mann- 

 lichen." 



We find among the Ciliata as demonstrated by several authors, 

 that many highly developed genera like Paramecium are true 

 hermaphrodites, and after conjugation separate as before, and we 

 also find true secondary males, as in Vorticella, and the like, 

 which pass entirely into the body of the female. It is quite 

 probable that these cases in which conjugation by absorption 

 occurs in Protozoa will be eventually explained as true sexual 

 union equivalent to fecundation by spermatozoa, whereas the 

 conjugation without absorption of the male form would necessa- 

 rily occur only between hermaphrodites which had not entered 

 upon so high a state of sexual differentiation, and belongs sim- 

 ply to the phenomena of fertilization by crossing. 



This is very near the same view as that taken by Engelmann 

 (Morph. Jahrb. i, p. 630) but differs in homologizing his Micro- 

 gonid or small male with a spermatozoon, and his Macrogonid 

 cr large female, with an egg, thus following out and applying 

 the terminology of Btitschli to the phenomena of conjugation 

 among Protozoa. 



Balbiani (Journ. de Micrographie, no. 8, 1882, p. 378) lays great 

 stress upon the fact that it is the whole animal among the Pro- 

 tozoa, which acts both as an egg and as a spermatozoon, and that 

 sexual differentiation takes place in the central germinative mass 

 of the body or cell, the nucleus becoming the female element, 

 and the nucleolus the male. He concludes, that a close compari- 

 son can be made between the discovery of the resorption or 

 disappearance of a portion of the nucleus, which takes place after 

 conjugation in Paramecium bursaria, and the expulsion of the 

 polar globules in the egg of Metazoa, and that a true female pro- 



