Nuclear Transplantation in Amoebae. I. - Journal of Cell Science

Lorch and Danielli—Nuclear Transplantation in Amoebae. I 451
specimens and were asked to place the unlabelled drawings into four groups.
The number of drawings placed in each group was recorded. Fig. 2 shows
a graphical representation of the sorting of drawings of 18 specimens of
A. proteus and 17 of A. discoides. The drawings were sorted five times on
different days by the same observer (J. F. D.). A similar graph was obtained
when four different observers sorted the same batch of drawings. 69 per cent,
of the amoebae were classified correctly as 'typical P' and 'typical D' respectively,
and 25 per cent, were placed in each of the categories 'like P' and 'like
FIG. 2. Graphical presentation of the results of repeated sorting of 35 outline drawings. The
percentage of drawings placed in each category is plotted. For explanation see text.
D'. For each group some amoebae were classified outside the species: 6 per
cent, of A. proteus drawings were classified as 'like D' and 6 per cent, of
A. discoides drawings as 'typical P'. Thus it seems that, although the method
of shape-sorting gives a clear-cut separation of the two species when cultures
are examined, there are always some individual amoebae which are atypical in
this respect.
Schaeffer (1916) states that the mode of formation of pseudopods is different
in A. proteus and A. discoides, and that 'the most distinctive morphological
characteristic of A. proteus is the possession of longitudinal grooves on the
surface when in locomotion'. These grooves are said to be 'never absent except
in such individuals as have not divided for many days'. Whereas we agree
that such 'grooves' are usually (though not always) seen in active specimens
of A. proteus, we cannot agree that they are never present in A. discoides.
They therefore cannot be used as an absolute distinguishing mark of A. proteus.
The same may be said of the other distinguishing features in the cytoplasm
of the two species as described by Schaeffer, e.g. shape, size, and number of
crystals present, number of refractile 'nutrition' spheres, speed of streaming,