APPENDIX, 



BOOK I. 



Page 8. Cell-formation by Rejwvenescence. In most cases the cell produced con- 

 tains only one nucleus, but several may be present, as in the zoogonidium of Vaucheria 

 and in the oosphere of those Saprolegnieae in which there is only one oosphere in the 

 oogonium. 



The ivhole of the protoplasm of the cell is not necessarily involved in this process, as 

 is shown by the development of the antherozoid in many cases. 



Page 9. In the process of conjugation in Spirogyra the nuclei of the conjugating cells 

 were observed by Schmitz (Sitzber. d. niederrhein. Ges. in Bonn, 1879) to coalesce. 



Page 10. From the researches of Schmitz on the Myxomycetes (Sitzber. d. nieder- 

 rhein. Ges. in Bonn, 1879), it appears that the nuclei of the cells which coalesce to form 

 the Plasmodium do not fuse but remain distinct : this case of coalescence of cells cannot, 

 therefore, be any longer regarded as an instance of cell-formation by conjugation. 



Free cell-formation. From the account of this process given in the text, it is evident 

 that the expression 'free cell-formation' is now used in a sense different from that which 

 it originally possessed. In its original sense it implied the development de novo of 

 fresh nuclei around which the protoplasm became aggregated so as to form cells: it is 

 now applied to those cases in which many nuclear divisions take place before any cor- 

 responding cell-divisions occur. Taken in this sense, free cell-formation differs only in 

 degree from cell-division, and it is not possible to distinguish sharply between them : 

 for example, the development of the pollen-grains of Dicotyledons is usually regarded as 

 coming under the head of cell-division, but it may equally well be considered to be a case 

 of very limited free-cell formation in which only four nuclei are produced by division 

 before any cell-division takes place. 



It must not be assumed that there is no such thing as a formation of nuclei de no'vo. 

 Strasburger (Bau u. Wachsth. d. Zellhaute) has pointed out that the appearance of the male 

 pronucleus in the oosphere during fertilisation (see p. 584) is an instance of it, inasmuch as 

 the nuclei of the pollen-grain do not pass directly into the oosphere, but break up and 

 become diffused either in the pollen-grain or in the pollen-tube. Johow has observed the 

 breaking-up and the reconstitution of nuclei in Chara (Bot. Zeitg. 1881). 



Page 12. For minute details as to the development of spores and of pollen-grains, 

 see Strasburger, Bau und Wachsthum der Zellhaute, 1882. 



Page 15. Cell-formation by Budding and Abstriction. Further instances of this are 

 afforded in the formation of the spores of Pellia epiphylla and some other Liverworts. 

 The mother-cell of the spores grows out into four protuberances, each of which becomes 

 shut off by a septum in the narrow pedicle and forms a spore (Strasburger, Zelltheilung und 

 Zellbildung, 1880). 



Page 16. Vegetati-ve Cell-formation. In the case of naked (primordial) cells division 

 takes place by the gradual constriction of the protoplasm : this has been observed by 

 Schmitz (Mittheil. aus der zool. Stat, zu Neapel, I, 1878) in the formation of zoogonidia of 

 Halosphcera viridis ; by de Bary in the amoeboid zoogonidia of Myxomycetes ; by Pring- 

 sheim in the oospore of (Edogonium ; and by Kirchner in the oospore of Folvox minor. 



Page 17. The Behaviour of the Nucleus during Division. The accounts of the structure 

 of the nucleus and of its behaviour during division given by Flemming and by Strasburger 

 do not agree in all points. The following are the principal differences between them : 

 (i) Flemming holds that the chromatin only exists in the form of fibrillae ; (2) he does 

 not agree with Strasburger that, in the splitting of the equatorial plate, any division of 



3 P 



