492 TRANSACTIONS OF SECTION D. 
coincides with that necessary for the support of the Wesenberg Lund-Ostwald 
theory. 1 . 
(3) There is no advantage to be gained by a planktonic animal whose specific 
gravity is greater than water increasing its superficial area during times of 
reduced viscosity. These points were explained at greater length in the Paper. 
FRIDAY, SEPTEMBER 6. 
The following Papers and Reports were read :— 
1. The Specific Histological Characters of the ‘ Luminous Cells’ of 
Pyrosoma giganteum and of Cyclosalpa pinnata. By Professor 
Cu. JULIN. 
In a recent publication’ I demonstrated the following facts: (1) The cells 
of the test (internal follicular cells of Kowalevsky, kalymmocytes of Salensky) 
of the egg of Pyrosoma giganteum persist throughout the whole of the develop- 
ment. At each of the principal resting-phases in the embryogeny, they show 
a characteristic topographical rearrangement in the egg. This rearrangement, 
this varying localisation, which I demonstrated for the first time, depends 
especially, at each of these stages, upon the abundant formation of these cells in 
distinct regions of the follicular epithelium of the egg. (2) The test-cells of the 
egg of Pyrosoma become exclusively and directly the cells of the paired luminous 
organs of the four ascidiozoids of the first young tetrazoid colony. This last 
and definitive localisation of the test-cells takes place during the last resting- 
phase of embryogeny. (3) Like the cells of the luminous organs of the 
primary and secondary ascidiozoids, the test-cells of the egg of Pyrosoma are 
luminous, and it is probable that this specific physiological property is correlated 
with the specific histological characters which these cellular elements possess in 
common. These test-cells may, therefore, as correctly be termed ‘luminous or 
light-producing cells,’ as much as the cells of the luminous organs of the 
ascidiozoids. (4) The specific histological characters common to both test-cells 
and the cells of the luminous organs of the ascidiozoids (both primary and 
secondary) of Pyrosoma consist essentially in the presence of a closely convo- 
luted tube in the cell-bodies, the wall of which is distinctly achromophile, and 
which is traversed by an achromophile reticulum, the meshes of which are filled 
with an albuminous liquid. On the reticular knots, and in immediate relation to 
this liquid, are numerous powdery granulations of nuclein, an albuminous sub- 
stance rich in phosphorus. This tube is entirely immersed in a small amount of 
liquid which fills the remainder of the cell-space. 
The results, both histological and experimental, obtained in the case of 
Pyrosoma, led me to examine whether such cells were present in the lateral organs 
of Cyclosalpa pinnata, which, as is known, are luminous. 
Very briefly, the results which I have obtained are as follows : The luminous 
lateral organs of both the solitary form of Cyclosalpa pinnata of the colonial 
form differ in structure from the luminous organs of the ascidiozoids of 
Pyrosoma. In the latter each luminous organ consists entirely of a mass of 
luminous cells quite free and independent of one another, immersed in the 
peripharyngeal blood sinus (pericoronary sinus). The cells are devoid of all 
nervous connection. In Cyclosalpa pinnata, agreeing with the description given 
by Fernandez, each lateral organ has its own framework of connecting cells, the 
freely-communicating meshes being filled with free blood-cells, the shape, form, 
and structure of which are very variable. Moreover, these cells, of which there 
is a considerable number, the specific character of which had not been recognised 
by Fernandez, have the distinctive character of the test-cells of the egg, and of the 
luminous cells of the ascidiozoids of Pyrosoma. They are, however, smaller 
than the latter. In the substance of the cell lies a tube, sometimes continuous, 
more frequently discontinuous, having numerous compact convolutions. When 
1 Zoolog. Jahrbiicher, Suppl. xv. 1 Bad. 1912, p. 775. 
