Jan., 1902 .] 
Variations in the Water-Snake. 
i8 3 - 
VARIATIONS IN THE WATER-SNAKE. 
Max Morse. 
The following is the result of a study of the variations in the 
members of a litter of 33 young of the water-snake — Natrix 
fasciata fasciata (L.) The mother was captured at the Lake 
Shore Railroad bridge No. 13, Sandusky, Ohio, in August, 1901. 
The head of the mother was so mutilated on being killed that it 
was thrown away, and hence no comparative study of parent and 
offspring could be made. The young were very nearly ready to 
hatch and probably would have been born in a few days. With 
the exception of some of the gastrosteges, all external characters 
were as in the adult condition. 
Owing to the want of time, only the external characters are 
considered in this paper. All measurements were made on the 
fresh specimens, i. e., before the snakes were placed in formalin. 
Care was taken not to stretch the specimens more than was 
necessary to straighten them. The counting of scales, etc., was 
done under a lens and each count was verified twice. 
The results of the study are given in the table on page 186. 
The following have been considered : 
1. The variation in length from snout to tip of tail. 
2. The variation in length from snout to the tip of the anal 
plate. 
3. The variation in length from anal plate to the tip of the tail. 
4. The variation in the number of gastrosteges, i. e., the 
ventral plates. 
5. The variation in the number of gastrosteges from their 
beginning in the gular region to the umbilicus. 
6. The variation in the number of postoculars. 
The maximum and minimum number, the difference between 
them, the mode and the mean are given in each case. Obviously, 
as the variates in columns 4, 5 and 6 are integral, the mean in 
these cases would sometimes be only approximate, i. e., fractional. 
Under these conditions the probable error of the mean was not 
calculated, but only approximated, by adding an integer to the 
mean in case the fraction was greater than one-half.* 
Comparing columns 2 and 3, it will be seen that there is greater 
variation in the bod}' region than in the tail. This is contrary to 
what may have been expected, as in certain organs, such as the 
vertebrae, greater variation occurs in the tail than in the body. 
In many cases the gastrosteges were found to be bifid, as in 
the normal anal-plate. The number of these that were found, 
together with their distribution, are given in column 7, where 
the numbers represent the number of the gastrostege, counting 
♦Davenport, C. B., “ Statistical Methods.” John Wiley & Sons, N. Y., 1S99. 
