684 REPORT — 1891. 



II. In apocytial fuiioi multinucleated masses of protoplasm (gametoids) may 



conjugate to Ibrm a zygotoid, by a sipliODOgamous process. The union 

 may be isogamous (most Mucorini), or anisogamous {M. heterogamus, 

 Vuill, some Chytridiece). 



III. Gametes may be classified as follows: — 



A. According to their formation — 



1. EuscHiST : formed by repeated complete divisions from a parent cell, 



the gametogonium. 



(a) EuTHTSCHiST : each nuclear division is accompanied by cell 



division, 

 (i) Bkabtschist : the nuclear divisions are completed before .any 



cell division takes place (spermatozoa of Liimbricus). 

 (c) IsosCHiST : the brood-cells of a gametogonium are all equal 



and functional. 

 ((Z) Anisoschist : the brood cells are imequal, some of them 



being reduced to aborted or degraded gametes (spermatozoa 



with ' nucleated blastophore/ ' ovum ' with polar bodies of 



most Metazoa). 



2. IlEMiscniST : the divisions are limited to the nucleus, none occurring 



in the cytoplasm (ovum with polar nuclei of many Arthropods). 



3. AroscHisT : the cell divisions do nor occur, but a cell directly assumes 



the behaviour of a gamete ( Volvo.f). 



4. SYiirHYTic : the gameto-nucleus is formed by the fusion of several 



nuclei (oogametes of Teronosjiorecc , isogametes of Dasgcladus). 



B. According to their behaviour, as — 



1. Facttltative : retaining the power of development if karyogamy 



fails to occur. 



2. Obligatory : witli no power of independent development. 



IV. Paeagenesis will include the following modes of rejuvenescence, usually 

 grouped under the terms ' parthenogenesis,' ' apogamy ' {pro parte), &c. : — 



A. Trite Paethenogenesis : the direct development of a facultative gamete 



without karyogamy. This may occur in the case of — 



(1) Isogametes; (2) Anisogametes, male (microgametes of iictocrtrj^e^), 

 and female ; (3) Oogametes (Lijjaris, drone egg). 



B. Simulated Paethenogenesis : — 



1. Cellular: a cell assumes directly the behaviour of a zygote (azy- 



gospores of Conjugattv). 



2. Aroci'TjAL : a multinucleate mass of protoplasm assumes directly 



the behaviour of a zygotoid (azygospores of Mucorini). 



C. Metagametal Rejuvenescence : — 



1. Unicellular: a single cell in the neighbourhood of the gamete 



assumes the form and behaviour of the zygote (formation of 

 ' ad\entitious embryos ' in embryo-sac of Funlua, Citrus, and 

 Ccclebogyne). 



2. Multicellular : a mass of cells in the position where gametes 



should be produced, assumes the character of the young organism 

 formed by the zygote ('Apogamy 'in prothallus oi Pteris cretica, 

 &c.). 



D. Paragamt or Endokartogamt : vegetative or gametal nuclei lying in a 



continuous mass of cytoplasm fuse to form a zygote nucleus. 



