470 Herr R. S. Bergh on the 



occurrence, and these have also been proved to appear, at any 

 rate in certain cases, in spermatoblasts*. Let us now con- 

 sider how long it has taken to increase our knowledge with 

 regard to these bodies ; let us further consider that it is now 

 gradually becoming possible to demonstrate the existence of 

 centrosomata in resting-cells also ; let us, moreover, remember 

 how greatly reduced in size the nucleus of the spermatozoon 

 usually is, and how difficult it must be to prove the presence 

 of a centrosoma in the spermatozoon should its bulk be propor- 

 tionately diminished f ; finally, let us reflect that a centro- 

 soma and a star-shaped figure appear near the male pro- 

 nucleus in the ovum. On considering all these points the 

 idea soon suggests itself that this centrosoma originates from 

 the spermatoblast and was present in the spermatozoon also, 

 altliough it is not always possible to demonstrate its existence. 

 As a matter of fact the origin of the centrosoma from the 

 protoplasm of the spermatozoon was actually maintained by 

 Boveri J also — an hypothesis which Kolliker imagined he 

 could " pass over in silence " {' Gewebelehre,' p. 67). That 

 Boveri's view nevertheless contained a grain of truth is 

 shown by the investigations of Fol {cf. below) . It is also 

 possible to arrive at a similar conclusion with reference to the 

 ovum. In the formation of the " directive bodies " very distinct 

 star-shaped figures appear both proximally and distally in the 

 majority of ova, from which we are entitled to infer the exist- 

 ence of centrosomata, the more so since these have been 

 positively demonstrated in certain cases §. Consequently 

 besides the female pronucleus a centrosoma must have 

 remained behind in the ripe ovum. 



As another argument in favour of the theory it is usually 

 alleged that the nucleus exercises a leading or directing influ- 

 ence in cell-division ; but it is altogether impossible to prove 

 this with reference to the cases which have been most closely 

 investigated. I will merely adduce the following instance : — 

 In the first two segmentation spheres of Ascaris megalo- 

 cephala^ with regard to which the excellent investigations of 

 van Beneden and Neyt, as also those of Boveri, are available, 

 the centrosomata divide, even before the nuclear contents have 

 differentiated into loops and the archoplasm (" sphere attrac- 



* E. g. by 0. Hertwig (" Vergleich der Ei- und Sainenbildmig bei 

 Neniatoden," Arch. £ mikr. Anat., 30 Bd., 1890). 



t It has recently been proved by an important paper by Platner that 

 centrosomata actually occur in the spermatozoa of certain mollusks (Arch, 

 f. mikr. Anat.i, 33 Bd., 1889). 



t Boveri, ' Zellen-Studien,' 2 Heft (Jena, 1888). 



§ E. (J. in the case oi himax by E. L. Mark (Bull. Mus. Comp. Zool. 

 Harvard College, vol. vi. no. 12, 1881). 



