692 McAllister . — Nttclear Division in Tetraspora lubrica . 
spindle is of the same general type which is found in the cells of the higher 
plants. In the Euglenidae, on the other hand, no recognizable spindle 
threads seem to exist, but nuclear division appears to be accomplished by 
means of a persistent c nucleo-centrosome 5 which divides, moves to the 
poles of the cell — each half with a group of chromatic bodies surrounding 
it. It is of interest here to note that this latter type of nuclear division, 
although occurring in the Diatoms and possibly in the Myxomycetes, has 
not been reported for any of the line of green plants arising with the 
Chlorophyceae. 
In view of the remarkable similarity in nuclear structure and division 
among all green plants, this wide difference in the character of the mitosis 
in these two orders makes it clear that no closer relationship exists between 
them than that due to a possible common origin from a remote ancestor. 
The Euglena type of nuclear division has not been reported for any green 
plant. It must be admitted, nevertheless, that Olive’s figures of mitosis in 
Empusa (38) show a striking similarity to the Euglena type of mitosis. 
This close similarity in the mitosis of such unrelated forms may suggest 
that data of a mitotic nature has little phylogenetic significance. The type 
of nuclear division so characteristic of the green plants is, however, so 
constant that it seems impossible to find an easy transition from it to the 
type characteristic of the Euglenidae. Thus the origin of the Chlamydo- 
monadaceae from the Eugenidae as suggested by Blackman and others 
seems excluded. 
It seems clear that in Tetraspora , although the chlorophyll-bearing 
protoplasm is definite and constant with regard to the position of the nucleus 
and pyrenoid, it is, nevertheless, not a highly differentiated protoplasmic 
body such as is to be seen in the plastids of Spirogyra, Oedogonium, 
Vaucheria, and the higher green plants. The chlorophyll-bearing area does 
not differ in texture or staining reaction from the other protoplasm. This is 
not in accord with Dangeard’s observations in Chlamydomonas (9) in which 
he believes that the chlorophyll-bearing protoplasm is alveolar, while that 
surrounding the nucleus is reticulate. Timberlake (47) believes that the 
protoplasm in Hydrodictyon is not segregated into a ‘ layer containing 
chlorophyll and one containing nuclei \ The form of the cells of this Alga 
prevents, however, positive proof of this point with living material, while 
with fixed material it is possible that, as is the case with Tetraspora, no 
distinction can be detected. It is not improbable, as Timberlake says, that 
more careful investigation of a large number of forms of the Chlorophyceae 
will reveal frequent cases in which highly differentiated chloroplastids are 
not present. 
