JuLy 14, 1899.] 
choplasm ’), distinct both from the general 
network and from the ground-substance, or 
are wholly new formations which, as it 
were, crystallize afresh out of the proto- 
plasmic substance. 
The second view is that of Butschli, who 
believes it to be applicable to all forms of 
protoplasm, and who has been followed by 
a considerable number of recent investiga- 
tors. Butschli’s interpretation differs en- 
tirely from the foregoing, the meshwork 
being regarded not as a network, but as an 
appearance resulting from the optical sec- 
tion of ‘alveolar’ or emulsion-structure. 
The spaces of the meshwork are drops of 
liquid occupying spherical spaces, or ‘al- 
veoli’; the ‘ fibers’ are optical sections of 
the thin layers, or lamelle, by which the 
drops, or alveoli, are surrounded. Even 
the astral systems receive the same inter- 
pretation, the astral ‘rays’ and ‘spindle- 
fibers’ being an optical illusion resulting 
from the radial arrangement of the alveoli, 
and hence of the inter-alveolar septa by 
which they are separated. 
The greater number of observers of pro- 
toplasm have given their adherence to one 
or the other of the two widely dissimilar 
views just outlined, though there are oth- 
ers t0 which we shall return later. Some 
investigators have taken a position inter- 
mediate between these two extremes. Thus 
Reinke has maintained that the cytoplasm 
of the echinoderm-ege is alveolar, as de- 
scribed by Butschli (though, as will appear 
beyond, he ascribes to this structure a dif- 
ferent physiological interpretation), while 
the astral systems are fibrillar, as held by 
Van Beneden, and arise as new formations 
at the cost of the alveolar walls. More re- 
cently, Strasburger has developed the re- 
lated, but still different, view that the cyto- 
plasm of the cell at large consists of two 
distinct substances, namely, the trophoplasm, 
or general nutritive plasma, which is al- 
veolar, and the kinoplasm, or the substance 
SCIENCE. 37 
active in division, which is fibrillar and 
gives rise to astral systems consisting of 
true rays and fibers. 
It is remarkable that the best observers, 
working in many cases at the same object, 
should have reached conclusions so diverse. 
It is obvious, further, that in the face of 
such contradictions it is impossible to give 
any discussion of the subject that is not 
more or less strongly tinged with the per- 
sonal views of the writer. Such views, by 
whomsoever expressed, can at present have 
no more than a provisional value; and this 
is the last subject on which dogmatism 
should be allowed. It is with full recogni- 
tion of these difficulties that I venture to 
state some of my own conclusions, partly 
because they may serve to explain, in some 
measure, to those who have not specialized 
in this field, how the existing diversity of 
opinion has arisen, partly because they 
have perhaps some bearing on the more 
general questions that were referred to at 
the outset. I shall take up in order the 
questions raised above. 
The Nature of the Meshwork.—Although in 
earlier papers I was inclined to regard the 
meshwork of the echinoderm-egg as a retic- 
ulum, further studies have left no doubt 
whatever, in my opinion, that in the resting 
cell it is in reality an alveolar structure—or, 
as I do not hesitate to call it, an emulsion— 
such as Butschlihasdescribed. I was firstled 
to this conclusion through the study of sec- 
tions of the eggs of sea-urchins ( Toxopneustes ) 
and star-fish (Asterias); but whatever doubt 
may have remained was completely dissi- 
pated by the study of the living eggs of 
Asterias (Fig. 1, 6), Echinarachnius, Arbacia, 
Ophiura (Fig. 2, a), under high powers. 
All of these eggs give in life essentially the 
same appearance, though no two are exactly 
alike. In all, the protoplasm consists of in- 
numerable closely crowded minute spheres 
suspended in a clear basis. The spheres 
may be called the alveolar spheres, or, more 
