74 MARCUS M. HARTOG. 
zygote in the same or allied forms. Logically, of course, all 
these being processes of rejuvenescence should have been 
treated earlier, but the foregoing discussion was necessary to 
the full understanding of the analysis of paragenetic phenomena 
which I now proceed to give. 
1. Trur ParTHENOGENESIS we define as the development of 
a single unfertilised (facultative) gamete. It occurs in the fol- 
lowing cases : 
a. IsocaMETES.—Not infrequently facultative. 
5. Microcametres.—Only known to be facultative in Ecto- 
carpus; the reduction of cytoplasm is too heavy a disadvan- 
tage for the resumption of active cellular life. 
c. Mrcacametes are more frequently facultative in the 
lower Algee and in Chara crinita. In other Metaphytes 
parthenogenesis isunknown. The only cases of true partheno- 
genesis of the Metazoan oosphere, differentiated as such 
by the formation of both polar bodies, are the following 
—lLiparis dispar and some other Lepidoptera, and Apis 
(Drone eggs). 
2. SIMULATED CELLULAR PARTHENOGENESIS occurs when a 
vegetative cell that might otherwise have formed a gamete 
assumes directly the behaviour of a zygote (‘‘ azygospores” of 
Conjugate, “ auxospores”’ of certain Diatoms). 
3. SIMULATED APOCYTIAL PARTHENOGENESIS occurs when an 
apocytial gametoid assumes the behaviour of a zygotoid (‘azy- 
gospores” of Mucorini). 
4. PROGAMETAL REJUVENESCENCE occurs when a progamete 
assumes the behaviour of a zygote. This is stated to be the 
case in many Arthropods where the ovum, after the expulsion 
of one polar body only, develops without fertilisation. Ac- 
cording to the recent discoveries of O. Hertwig and Boveri, 
many cases referred to this (if not all) should be placed under 
the following heading. 
5. MrTraGAMETAL REJUVENESCENCE is the best term I can find 
to fit the case of certain flowering plants (Celebogyne, 
Citrus, Funkia, Nothoscordum), where the tissue-cells 
adjoining the apex of the embryo-sac grow into it, and 
