THE PLASTOGAMY OF ACTINOSPHARIUM. 
HERBERT P. JOHNSON. 
In his valuable and interesting exposition! of the phenomena 
of fertilization, Hartog briefly describes what he considers the 
most primitive type of the process—the union of two cyto- 
plastic elements, without accompanying nuclear fusion. This 
he calls plastogamy, and says in regard to its 
«Jn the true myxomycetes plasmodial fusion always precedes 
spore-formation. Possibly, as has often been suggested, plas- 
modial formation has led to the various modes of karyogamy. 
The nuclei pass freely from place to place in the plasmodium, 
and may eventually be far removed from what was their original 
cytoplast ; and the cytoplastic elements again undergo a reor- 
ee by their fusion. . . . In this ii is fulfilled what I 
pene and cytoplast that are stances to each other.” 
What may be termed accessory plastogamy necessarily occurs 
in many kinds of fertilization where the essential factor is 
unquestionably karyogamy. Instances of this are the formation 
of a zygote by the union of two zoospores, and the coalescence 
of the microgamete with the megagamete in the conjugation 
of Vorticellids. Even among the Metazoa it is maintained by 
Verworn 2 that the cytoplasmic as well as the nuclear part of 
the spermatozoon is not without its influence in the fecunda- 
tion of the egg. 
True plastogamy is characterized by non-fusion of nuclei. 
It is necessarily a simpler process than karyogamy, and occur- 
ring as it does only among the lower Protozoa and Protophyta, 
may well be regarded as the precursor of nuclear fecundation. 
The significance of plastogamy is still very obscure, and it is 
extremely probable that it is not the same in all cases. The 
1 “Some Problems of Reproduction.” Q. J. M. S., xxxili, pp. I-79, 189l. 
2 Arch. f. d. ges. Physiol., li, p. 98, 1891. 
