JUNE 21, 1901.] 
intimate of causal relations have been in- 
ferred, in spite of the existence of many 
forms of reproduction not so preceded. From 
the morphological standpoint there is every 
gradation from parthenogenesis or the de- 
velopment without fertilization of cells 
which are normally fertilized, to the sim- 
plest case of plants multiplied by branching 
root-stocks. From the evolutionary stand- 
point such differences are of comparatively 
little moment; all organisms seem to be 
variable, whatever their methods of repro- 
duction. There is, however, a general law 
that the more specialized the organism 
and its reproductive processes the smaller 
are the probabilities that conjugation can 
be dispensed with. It is as though com- 
plexity of organization required a higher 
tension of the protoplasmic structure which 
could not be maintained without conjuga- 
tion, rest or change. Thus among animals 
of high organization there are but two con- 
spicuous instances of normal partheno- 
genesis, the bees and the plant-lice, and in 
both of these the generations, sexes or 
castes produced without conjugation are 
inferior, specialized and unable to main- 
tain the existence of the species. The rela- 
fission of Metazoa are adjustments having only an 
outward resemblance to the budding and fission of 
Protozoa.”” While processes, like organisms, must 
have a common origin if genuine homologies are to 
be established, it seems obvious that on the plane of 
Professor Hertwig’s discussion conjugation and repro- 
duction are directly comparable taroughout organic 
nature. Current errors are not so much in the direc- 
tion of mistaking the nature of the processes, as in 
failing to observe that what is termed “asexual re- 
production’ in simple organisms is generally called 
‘erowth’ in the more complex. From the cytolog- 
ical standpoint there are two sets of phenomena in 
both plants and animals, conjugation or fertilization 
and fission or growth by cell multiplication. The 
association and specialization of cells in compound 
organisms (Metazoa and Metaphyta) have given rise 
to a great variety of independently acquired repro- 
ductive adaptations superposed upon conjugation and 
fission, but different in category, and having neither 
phylogeny nor homology with those processes. 
SCIENCE. 
975 
tive frequency with which parthenogenesis 
and asexual reproduction are maintained 
among the lower animals and plants, in 
connection with parasitic or saprophytic 
habits suggests the further possibility that 
protoplasmic compounds of high complexity 
may be utilized as partial or complete sub- 
stitutes for conjugation. Cytologists might 
thus find it worth while to ascertain, if 
possible, the exact nature of the protoplas- 
mic relations between parasite and host. 
CHEMICAL AND MECHANICAL THEORIES. 
Chemical theory has advanced to the 
point where different qualities of compounds 
are explained by reference to positional re- 
lations between the component atoms, but 
behind this lies the question of the nature 
and qualities of the elemental substances 
themselves. By common consent the molec- 
ular constitution of protoplasm is admit- 
ted to be almost unimaginably complex and 
still utterly inaccessible and intractable from 
the chemical side. Nevertheless, we recog- 
nize that the qualitative or potential dif- 
ferences of protoplasm extend not only to 
species, but actually to individuals, and yet 
some biologists are attempting to grasp 
these ultimate differences before solving 
the problem of the physical and the chem- 
ical groundwork of protoplasmic structure. 
A solution of evolutionary problems on 
this basis can be expected only by those 
who remain regardless of the fact that the 
already insurmountable physical and chem- 
ical difficulties would be, as it were, multi- 
plied by infinity under theories which 
imply that not only the complexities of the 
organic constitution, but also the endless 
details of individual difference, are sym- 
bolized, materialized or predetermined by 
positional or other relations of atoms, to 
say nothing of the chromosomes or granules 
which some have taken to be the actual 
organs of protoplasmic foreordination. 
Similar theories invented by theologians 
