290 
CARNEGIE INSTITUTION OF WASHINGTON 
was undertaken. The sabellid, Euratella chamberlin, 1 used in these experi¬ 
ments has not previously been reported from this region although it is 
found in large numbers in the moat at Fort Jefferson. 
Two groups of these worms were exposed simultaneously for varying 
periods in order to compare the differential effects of the rays. One group 
received the full output of beta and gamma rays from 123 mg. of radium. 
The other group was screened by a lead plate and received only gamma 
rays. The number and appearance of the new segments formed in pos¬ 
teriorly regenerating control-worms was the same as previously reported. 2 
After removal of 4 to 6 anterior segments, normal worms regenerate only 
the head and collar segments at the cut surface. Histological examination 
of preserved material is necessary to discover whether the thoracic seg¬ 
ments are replaced by transformation of abdominal segments as Berrill 3 
reported in Sabella pavonina. 
After 100 hours exposure to beta and gamma rays, the worms fail to 
replace anterior or posterior segments, though similar exposure to gamma 
rays alone has little effect upon regeneration. Apparently, therefore, the 
beta rays are chiefly responsible for the failure to replace lost segments. 
Sections of worms receiving the combined beta and gamma radiation show 
that wound healing is effected by rearrangement of adjacent old tissues 
without formation of new material. The new segments at the posterior 
ends of normal regenerating worms are mainly epithelial in origin. The 
epidermis and gut lining arise by proliferation of material from similar 
old tissues, while the nerve cord and mesodermal structures are formed 
from epidermal cells that push into the body cavity at the tip of the 
regenerating region. No undifferentiated reserve cells are found in Eura¬ 
tella chamberlin , although they are a source of new material during regen¬ 
eration in other polychsetes. The loss of regenerative powers after radiation 
in this worm is apparently due to direct effects of the rays within the 
epithelial cells. 
Study of the Reef Corals of the Tortugas, by John W. Wells 
The period of ten weeks, from June 1 to August 8, was spent at the Tor¬ 
tugas Laboratory. The study of the reef corals of the Tortugas was under¬ 
taken in connection with my work on fossil corals, a knowledge of the living 
corals and coral reefs being of great value in the interpretation of the more 
obscure fossil forms. The areal and bathymetric distribution of the dif¬ 
ferent species, as well as the different growth-forms assumed under different 
conditions, was particularly emphasized. A total of 24 species (including 
two varieties or subspecies) of Madreporaria having a bathymetric range 
from low-water level to a depth of 25 feet was collected and examined. 
The distribution of the several types of associations of reef species was 
plotted on a chart of the Tortugas area. 
During the dredging trips of the Anton Dohrn, specimens of eight species 
of “deep-sea corals” were taken in three hauls—at 39, 43 and 582 fathoms. 
Experiments were conducted in an effort to determine the toleration of 
reef corals to increased salinity of sea-water. Specimens of the commoner 
reef species were placed in vessels containing sea-water evaporated to vari¬ 
ous concentrations, the salinity being roughly determined by titration. 
1 Identified by Dr. J. P. Moore, University of Pennsylvania. 
' 2 Carnegie Inst. Wash. Year Book No. 30, p. 395, 1930-31. 
3 Berrill, N. J., Jour. Exper. Zook, vol. 58, p. 495-523, 1931. 
TORTUGAS LABORATORY 
291 
All of the specimens were placed in the water for 12-hour periods except 
in the case of salinity 50 + , when the period was 6 hours. The results of 
these experiments are summarized in the following table: 
Species 
Salinity 
40 + 
43+ 
46+ 
50“ 
50+ 
55“ 
70- 
Eusmilia fastigiata. . . 
Unin- 
Unin- 
Dam- 
Re- 
Killed 
jured 
jured 
aged 
covered 
Oculina diffusa ... 
Killed 
Orbicella annularis .. . . 
Unin- 
Killed 
Killed 
Killed 
Killed 
Re- 
Killed 
Killed 
jured 
covered 
Orbicella cavernosa. .. . 
Unin- 
Do. 
Do. 
jured 
Favia fragum . 
Unin- 
Do. 
Unin- 
Unin- 
Unin- 
Injured 
Killed 
jured 
jured 
jured 
jured 
Mceandra areolata. . . . 
Do. 
Do. 
Do. 
Unin- 
Do. 
Do. 
Unin- 
Killed 
jured 
jured 
Mceandra strigosa . 
Do. 
Do. 
Do. 
Do. 
Do 
Do 
Mceandra clivosa . 
Do. 
Do. 
Unin- 
Unin- 
Do. 
Do. 
Do. 
Do. 
jured 
jured 
Agaricia agaricites 
crassa .. 
Do. 
Dam- 
Killed 
Killed 
Re- 
Killed 
aged 
covered 
Siderastrea radians. . . 
Do. 
Unin- 
Unin- 
Unin- 
Unin- 
Unin- 
Re- 
Killed 
jured 
jured 
jured 
jured 
jured 
covered 
Siderastrea siderea. . . . 
Do. 
Killed 
Re- 
covered 
Porites porites . 
Unin- 
Do. 
Killed 
Killed 
Killed 
Killed 
Killed 
jured 
Porites furcata . 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Porites astreoides . 
Do. 
Do. 
Do. 
Do. 
Do. 
In- 
jured 
Acropora muricala ... . 
Killed 
Killed 
These experiments, although of a preliminary nature, show that the 
hardier species of reef corals— Favia fragum, Mceandra areolata, M. clivosa, 
M. strigosa and Siderastrea radians —can endure a considerable increase in 
salinity at least for short periods of time, that most of the other species are 
killed by salinities in excess of 45, and that all are soon killed by a con¬ 
centration greater than 55. It is probable, as Vaughan has inferred, that 
the reef corals of the Tortugas will not endure a concentration greater than 
the highest recorded for Tortugas water—36.29, for any considerable length 
of time. 
Studies on the Nematodes of Tortugas Fishes> by O. L. Williams 
More than 800 fishes representing about 175 species were examined for 
internal parasites during the summer of 1932. Although a careful study of 
the nematodes collected must be made before many conclusions can be 
drawn, a few preliminary observations may be recorded here. 
A sufficient number of hosts has been examined to demonstrate rather 
clearly that the incidence of infestation with nematodes is somewhat lower 
in the fishes of the warm, shallow waters about the Tortugas than is the 
case in either the cooler, deeper waters of the same region or the cooler, 
shallow waters found farther north. Nematodes were collected from a 
