Pomona College, Claremont, California 147 
newly emerged young were shell pink and shiny. After emerging 
from the egg sac they moulted and at three days of age had a light 
brown cephalothorax with black eye space, light brown legs and 
spinnerets and a reddish brown abdomen. The legs, abdomen and 
spinnerets were covered sparsely with dark hairs. The trapdoor 
spiderlings were so slow in changing that the moults occurred about 
a month apart. At the age of one month and three days the young 
had grown slightly larger, the cephalothorax was light brown with 
darker brown in the cervical groove. There was a brown line 
from the black eye space down to the first groove ending. The legs 
and spinnerets were the same color as before. The abdomen 
was colored a little darker brown and six light spots were on the 
middle surface of the abdomen. The spinnerets were shorter than 
at the three-day stage. At the next moult (two months and six 
days), the shape and coloring of the spiderlings had changed con- 
siderably. The cephalothorax had elongated, the color was red 
brown, the eye space black. The abdomen had become smaller and 
the spinnerets disappeared from sight. The color of the abdomen 
was dark reddish brown with numerous flecks of lighter brown over 
the surface of the abdomen. The legs and palpi were gray brown. 
At three months and six days the whole spider had changed from the 
reddish brown color to the chocolate brown. The cephalothorax 
was chocolate brown with black eye space. The abdomen had 
become the shape of the adult’s and was a dark chocolate brown 
with numerous horizontal ridges. The legs were gray brown. At 
the age of four months the young had taken all the color of the 
adult, though their size was only one-tenth that of the mature spider. 
There is in the collection a specimen of Bothriocyrtum of about a 
year’s age. It is three-fourths the size of the adult, and though its 
sex is not differentiated yet, it has all the adult coloring. From 
these observations it is concluded that it must take several years 
for the spider to reach maturity. 
The conclusions reached after the study of these families of 
spiders may be stated in a few paragraphs: 
1. The young in all cases resemble the adult in shape of body, 
placing of eyes and in habit. This was true of the young just 
emerged from the egg sac as well as the older ones. The shape of 
