SOME PROBLEMS OF EEPRODUCTION. 605 



sense, it denotes a process of cellular (or nuclear) fusion, and 

 is better designated as " syngamy." 



3. The terms " sexuality, sexual," etc., have been used 

 also ambiguously, and would be advantageously (a) replaced 

 by '^syngamy " and its derivativ^es where no binary differen- 

 tiation is necessarily implied, or (b) only used with the prefix 

 " binary " where such differentiation is intended, 



4. Syngamj' is not necessarily associated with germination ; 

 on the contrary, in the most primitive types the cell freshly 

 produced by syngamy (the zygote) passes into a condition of 

 rest, or gives rise only to a limited brood of resting-cells, 

 which will only germinate after the lapse of time and under 

 favourable conditions. The formation of a membrane round 

 the oosphere at the onset of .syngamy in Metazoa and Meta- 

 phytes is probably the last trace of this, the original con- 

 sequence of syngamy. 



5. Syngnmy includes internal karyogamy and merogony 

 as well as the pairing of .'separate individual cells. It seems 

 possible that in the Alcyonarians the oosphere is non-nucleate, 

 and that the nucleus of the oosperm is exclusively male, as in 

 that produced by merogony. 



G. Progamic cell-divisions come under three formulfe : 



(a) Gametes are morphologically equal to zoospores, and 

 are therefore produced by multiple cell-divisions. 



(?>) No tissue cell ever becomes directly transformed into a 

 gamete. 



(c) Karyogamy (with the possible exception of the Basidio- 

 mycetes) is never possible where both the pairing-cells (or 

 nuclei) have had a share in active cell-life or growth. 



7. Progamic divisions and reducing divisions, though some- 

 timescoincident (as in Metazoa), are not necessarily associated, 

 but may be widely divided in the life-cycle where there is 

 '^antithetic alternation of generations." 



8. The germ formed by parthenogeny or merogony can 

 double the number of its chromosomes. 



