SOME PROBLEMS OF REPRODUCTION, 27 
gametes by binary fission. Owing to the subterminal position 
of the nucleus in the cell at the time of mitosis one daughter- 
nucleus has too little cytoplasm around it for further evolu- 
tion, and so forms an arrested gamete, while its sister gets 
the lion’s share, and enters into karyogamic union with the 
Fie. 1.—Conjugation of Basidiobolus : a, early stage; 4, division of each cell 
to form active and arrested gametes; c, formation of zygote. I use 
here the nuclear notation explained above. 
corresponding gamete of the other pair. So we describe the 
process thus: the adjacent cells are progametes, each of which 
by unequal divisions forms two gametes, the apical one 
arrested, the other functional. 
The Mucorint1, in the common phrase, form zygotes by the 
isogamous union of gametes, save in one species, Mucor 
heterogamus, Vuillemin, which is anisogamous. But this 
description is not at all accurate from the present standpoint 
of cytology ; for “ gametes” and ‘ zygotes,” so called, are 
not cells, but apocytia of plurinucleate protoplasm in a cell- 
wall, which we may term “ gametoid” and “ zygotoid”’ re- 
spectively. Of the nuclear changes involved in the conjuga- 
tion we know as little as in the Chytridiex. Several 
possibilities are open : 
(1) The nuclei of the respective gametoids may unite two 
and two within the zygote in exogamous union ; 
(2) The nuclei may unite in pairs or otherwise, irrespective 
of their origin ; or, finally, 
(3) Rejuvenesceuce may ensue, as in plasmodial formation, 
