174 DONALD WALTON DAVIS 
indicated in the table, are such as would result from successive 
simple divisions. The condition of no. 21 is conclusive in this 
respect, the evidence from nos. 19 and 20 being less positive 
because of loss of parts. I have found no instance of division of 
an animal into three parts giving rise to but three regenerating 
regions, as would be expected in case of a single compound 
division. 
One might expect to find that specimens dividing into more 
than the usual number of pieces would be shown to have had an 
unusually high number of old mesenteries. Such, however, is 
not the case. Only no. 17 possessed, before division, a high 
number of complete mesenteries. The average for specimens 
included in table 5, omitting nos. 19 and 20 on account of missing 
parts, is 13.5 complete mesenteries. The average for specimens 
dividing into two parts, included in tables 3 and 4, is 16.4. 
Evidently, then, the close recurrence of fission is not correlated 
with a high number of complete mesenteries. Indeed, it seems 
to be related rather to a number lower than the average; and it 
eventually tends through generations to raise the number of 
mesenteries higher than does the more common simple division. 
As will appear from the statements below, multiple fissions are 
not associated with particular numbers of siphonoglyphs and 
pairs of directive mesenteries. 
Tables 3 to 5 record the divisions of twenty-two polyps. 
Seventeen of them were diglyphic before division, three were 
apparently triglyphic, one was monoglyphic and one tetraglyphic. 
In thirteen cases a diglyphic individual separated into two parts, 
each receiving a pair of directive mesenteries. One of the di- 
glyphic specimens (no. 17) divided into three parts and another 
(no. 19) into four parts. In both of these cases one pair of 
directives passed to each of two of the resulting pieces, and one 
or two pieces contain no old directives. Another of the di- 
glyphic specimens (no. 16) divided into two parts, one with two 
pairs of directive mesenteries, the other with none. Still an- 
other of the diglyphic individuals (no. 21) divided into three 
parts, one part with one pair of directives and a single bounding 
directive, one part with the corresponding bounding directive 
