360 
Fig. 2. Curve B shows the extreme trailing blue por- 
tion of the column chromatogram. The paper chro- 
matographic curves are indicated by small letters. The 
curves of the rhodanite pink (r), the lavender (1), and 
the calamine blue (b) regions were read from weak 
solutions produced by eluting dried papers. 
chromophores as a single coplaner chromo- 
phore.” The curves he used as examples com- 
pare markedly with the curves of aplysia 
purple. 
The writer has not yet found a satisfactory 
explanation for the instability of the D band 
absorption peak, which seems quite sporadic 
in its variation but doubtless follows well- 
defined laws. 
Schreiber’s work (1932) on the Mediter- 
ranean purple-producing Aplysia indicated 
that the peak in the F band (at approximately 
500 m^i) represents the absorption by a sub- 
stance similar to urobilin, and that the other 
peak in the high 500 region (Schreiber’s 
broad unstable D band) represented the pre- 
cursor of this substance. The above data con- 
firm his theory. 
It seems that the fast-growing young do 
not possess as much of the red finished 
product as do the adult specimens and hence 
secrete a larger percentage of the blue precur- 
sor substance. No basic differences other than 
that of relative quantity of the substance and 
its precursor are indicated by the spectro- 
photometric studies. 
PACIFIC SCIENCE, Vol. XIII, October, 1959 
The condition of the individual animal is 
indicated as being highly influential in this 
respect as well. Well-fed adult specimens 
seem to have an excess of purple which is 
secreted at the slightest provocation, and of- 
ten with no provocation at all. 
The vertebrate bilins are derived from the 
breakdown of the tetrapyrrole molecules of 
hemoglobin. However, in plants tetrapyrrole 
molecules are the basis of chlorophyll. The 
quantities of aplysia purple produced would 
indicate a plentiful source such as chloro- 
phyll, which is consumed in quantity by 
these algae eaters. 
The bilichromes of the red algae may well 
be an additional rich source of the purple, as 
suggested by Fontaine and Raffy (1936). This 
is supported by the fact that adult animals 
feeding largely on Plocamium pacificum, which 
has a low chlorophyll but a high phycobilin 
content, usually produce a much greater 
quantity of pigment and with less provoca- 
tion than those subsisting on other algae. 
Fig. 3 . The absorption spectra of the red (A), and 
composite lavender and blue (B) regions from the col- 
umn separations. After the solution giving curve B had 
been in the refrigerator for two weeks it had changed 
its gross color and produced the curve marked C. 
