h and k, pp. 212 to 213). On Apirl 21, 1949, 
the date of observation, one was 297 and the other 
324 days of age. Both had similar histories of 
many wounds received from their associates. On 
this date each had an open purulent wound over 
the sacrum approximating 2 square inches. Dur- 
ing the previous winter one had an open purulent 
wound over the scrotum. This was healed by 
April and the testes descended in a normal manner. 
The other rat had received much more damage to 
the genital region. During the previous fall it 
received a warble infestation of the scrotum. 
Following emergence of the adult fly the penis was 
left protruding posteriorly outside of the sheath; 
one testis was destroyed. The other testis was re- 
duced in size, and even during the warm spring 
weather it rarely descended into the healed scro- 
tum. The behavior noted was close following, of 
the type associated with a receptive female, mild 
boxing, hip-bumping, and momentary mounts. 
The other three cases of homosexual behavior 
involve females. On June 30, 1948, my notes 
record the fact that a 113-day-old female was 
courting 318-day-old female 33. No details of the 
behavior were recorded. On April 25, 1949, 403- 
day-old female 63 was seen to smell and paw the 
genital region of 297-day-old female 733 for several 
seconds. This was the only observed instance of 
such a marked genital inspection of one female by 
another, in the fashion normally exhibited by 
males. The third instance was between two 284- 
day-old sisters. On May 26, 1948, the date of the 
behavior, female 42 was in her 10th day of lacta- 
tion, while female 43 was in the terminal stage of 
pregnancy — she delivered 5 days later. Ten 
minutes before the beginning of their relationship, 
female 42 had chased senescent (circa 644 days of 
age) male 12 out of the Food Pen, across the alley, 
and into Area III. The behavior between the two 
females occurred in the Food Pen just in front of 
the activity recorder at Passage 7. Each dragged 
her genital region over the ground, across a stick, 
and rubbed her sides against the sides of the re- 
corder. They also kept sidling up against each 
other. Female 42 kept throwing her rear against 
and occasionally on top of female 43. Occasion- 
ally one would paw or nudge the other’s body, but 
mainly the sidling and nudging activity was most 
conspicuous. Occasionally female 43 would jump 
away from female 42, as if not too sure she could 
court her. This activity lasted for about 10 
minutes. Adult male 22 came in the Food Pen 
shortly after they broke up. He smelled where 
they had been, but otherwise paid no attention to 
them. There was no evidence in the observations 
of this and the following day these females were 
attractive to males. 
Females, who are themselves not attractive to 
males, do inspect signposts left by females who 
are attractive to males; however, none exhibit 
any of the rolling, rubbing, dragging, etc., which 
is characteristic of males. Initial attempts to cor- 
relate behavior with known states of the estrous 
cycle, as indicated by vaginal smears, had to be 
discontinued. Avoidance of traps, which pre- 
cluded recapture, was a practical problem. A 
more serious reason for discontinuing vaginal 
smears was the obvious disturbance to the rats 
as a result of capture and handling. I was fearful 
that excessive trapping would disturb the physiology 
of the rhythm. Trapping definitely did alter 
maternal behavior in relation to new-born young. 
An attempt was made to ascertain the relation 
of the behavior of males to known states in the 
estrous cycle of a female. Scent was obtained from 
a hooded laboratory rat, No. 44, whose estrous 
cycle was being followed by vaginal smears in Dr. 
Curt P. Richter’s laboratory. Each morning a 
clean metal pan was inserted under the cage. 
On the following morning 50 cc. of a 50 percent 
alcohol-water solution was sloshed around in the 
pan for several minutes over the urine and feces 
deposited during the previous 24 hours. Each 
day’s solution was kept in a separate jar. Samples 
were obtained from June 2 to 11, 1948. This 
female was in estrous on June 5 and 10. 
Four irregularly oval rocks, about the size of an 
adult rat’s body were placed in a line down Path 1 
on June 29, 1948. The rocks were at 2-foot inter- 
vals. The contents of the jars for June 2, 4, 5 
(estrous), and 6, were poured over separate rocks 
at 5:15 p.m. During the next 45 minutes four 
males approached. Each smelled one or all of the 
rocks before proceeding away. During this time 
the rocks were still obviously wet. The evaporating 
alcohol probably served as a repellent. Male 22 
was the first male to be excited by the rocks. 
This was 80 minutes after the solution had been 
poured on them. He smelled at each and walked 
over each dragging his genital region. There was 
no differential response. Male 47 approached a 
few minutes later and responded likewise — with 
the exception that he twice drug over the rock for 
June 4 (the day before estrous). He immediately 
