76 Vitality and Organization of Protoplasm. 



I ually became inclosed in one of the blastonieres, coalesced with its nu- 

 1 cleus. Segmentation was thus nowise influenced by the non-participa- 

 tion of the spermatic nucleus, and the non-nuclear portion of the sperm- 

 atozoon proved to be here the active agent in the bisexual ontogenetic 

 process. Similar occurrences were witnessed by Teichmann (a). And 

 numerous observations have confirmed in many classes of animals that 

 the formatively active portion of the spermatozoon, the portion in which 

 the centrosomes arise, and around which the astrospheres form, is the 

 medial, non-nuclear portion. ■ This agrees entirely with the fact, that 

 in mitotic division in general the process starts and is actively governed 

 ^ by extra-nuclear centrosomes. 



Important to the contention here dwelt upon is the observation of 

 Wilson & Mathews (b) and others, confirmed as occurring in all classes 

 of animals examined; the observation, namely, that after entrance into 

 the egg the spermatozoon turns completely round, so that the head 

 comes to face the circumference of the egg, whilst its base or medial 

 portion develops under granular commotion the centrosomes with their 

 astrospheres, and penetrates in this position under constant activity into 

 the interior of the egg-plasm, proving thereby that the non-nuclear, 

 medial portion of the spermatozoon is the real bearer of vital and form- 

 ative activities, E, Hertwig, v. Erlanger and others have come to the 

 conclusion that the medial part of the spermatozoon and the developed 

 *C centrosomes have to be considered as essentially identical in substance. 

 And this really means that the formative process starting around the 

 centrosomes involves the entire medial plasm, while it is gradually in- 

 volving all non-nuclear egg-plasm, and finally also all nuclear plasm. 



The experiments on segmentation and development of artificially 

 fertilized portions of egg-plasms initiated by E. and 0. Hertwig and con- 

 tinued by Boveri, Morgan, Ziegler, Delage and others go likewise to 

 show that the centrosomes have power without the aid of the nucleus 

 to actuate and control the process which gives rise to segmentation. 

 Boveri found, moreover, the non-nuclear portions of the egg-plasm of 

 Echinus in which a spermatozoon had penetrated undergo segmentation 

 solely under the influence of the activity of the centrosomes without 

 fhe aid of nuclear chromatic substance whatever. And Ziegler* ob- 

 served that in a normally fertilized egg the entire nuclear substance of 

 both united nuclei remained confined in one of the blastomeres, whilst 

 in the other blastomere there remained only the corresponding centro- 

 / some with its astrosphere. Thereupon further segmentation took place 



a. Ueber Furehimg Befruchteter Seeigeleier ohne Betheiligung des Sponiui- 

 kerns," Jenaische Zeitschrift fiir Naturwiszensehaft, B. 37, 1902. 



b. "Maturation, fertilization and polarity in the Echinoderni egg. Journ. 

 Morph., V, 1895. 



*Furch\ing ohne Chromosomen. Arch fiir Enter. Mech B, 1898. Living 

 far away from any public biological library, I have not been in a position to 

 verify all quotations from the original papers, but relied in many of them on 

 Korsclielt and Ileider's splendid "Lehrbiich," 1893. 



