828 The American Naturalist. [September, 
of a species of this genus of Urodele batrachians. They were placed 
in the aquaria of the biological school, and a goodly number were 
hatched out, but some of the ova were attacked by a unicellular green 
alga, which multiplied rapidly upon the zona radiata, and between the 
latter and its thick gelatinous covering, in a single layer. These algse 
probably intercepted the oxygen. At any rate the embryos in all the 
eggs thus affected eventually died before their escape from the egg. 
The embryos which had just hatched were found to be exceedingly 
interesting subjects in which to observe karyokinesis, or indirect cell- 
division. Nuclear spindles could be readily detected in all the tissues 
of the body in the greatest variety of stages. A few days after hatch- 
ing the nuclear spindles became far less abundant and not so easily found. 
In sections of just-hatched embryos one could find nuclear spindles in 
all the tissues of the body, though most rarely in the muscles. They 
were particularly well-shown in the tissues of the brain, spinal cord, 
cranial ganglia ; the prechondral tissue masses, from which the carti- 
laginous branchial bars are formed ; in the blood corpuscles both in 
the vessels and heart ; in the connective tissues, and in the epidermis, 
as well as even in the notochord. The epidermis of the young Triton 
or Salamander has been commended for the purpose of illustrating 
karyokinesis in the laboratory by European teachers of histology. It 
is, therefore, with much pleasure that I point out the occurrence of a 
type in this country which is tolerably abundant and accessible, which 
serves even a better purpose, as it illustrates the fact that karyokinesis 
is universal, or holds with respect to all of the tissues of the body dur- 
ing the early stages of development. 
This type is also well adapted for the purposes of elementary teaching, 
in that the cells and muscle-fibres are very large, so that the spindles 
are likewise very large. The filaments of chromatin are also very 
large, thick and sharply defined, so that all of the phases of nuclear 
metamorphosis may be readily traced with moderate powers of the 
The method of preparation which I found to serve my purpose very 
well was as follows : The embryos were killed and hardened with 
corrosive sublimate or Kleinenberg's picro-sulphuric acid. After 
hardening and thorough washing in repeated changes of weak alcohol, 
if corrosive sublimate is used, or in 70 to 80 per cent, alcohol if 
picro-8ulphuric acid is used, the embryos are stained in toto in a dilute 
solution of haematoxylin ; Kleinenberg's or Delafield's answers admir- 
ably, though even a simple saturated solution of extract of logwood 
in alcohol, saturated with potash alum, also gives good results, but not 
