TWINNING AS A MODE OF REPRODUCTION 207 



II. Sexual reproduction 



a) In Protozoa {l^'^'^f^^^^g^^^^ 



(the typical fertilization process 

 herma phroditism 



Such a classification, while in most respects logical, 

 is incomplete, and fails to take account of mitosis, 

 twinning, and polyembryony. At the risk of being 

 considered venturesome, I wish to present for consider- 

 ation another classification of modes of reproduction 

 that seems to me, in some respects at least, more workable 

 than those previously proposed. 



MODES OF REPRODUCTION 

 I. Axiate reproduction 



A TT • 11 1 /^^ Mitosis in both Protozoa and Metazoa 



A. Unicellular l^j Amitosis in both Protozoa and Metazoa 



B. Multicellular 



rjy r ' \c) In embryos 



1. Transverse fission |^) j^ ^^^^/^ 



2. Lateral budding 

 'a) Fission of blastoderm before axis of 



symmetry is laid down 

 h) Production of two (or more) axes through 



plural gastrulation 

 c) Bilateral fission of the right- and left-hand 



primordia of a single embryonic axis 



11. Non-axiate reproduction 



(a) Gemmulation 

 h) Stotoblast formation 

 c) Sporulation 

 a) Parthenogenetic 

 i. Paedogenetic 

 ii. Adult 

 h) Syngamous 

 i. Isogamous 

 ii. Heterogamous 



3. Twinning 



B. Gametic 



