lvi CHARLES OTIS WHITMAN 
more primitive than the scattered sense cells (goblet cells, labial 
sense cells and Bayer’s organs) and that they cannot have been 
derived from aggregations of. the latter, as had been maintained 
by Maier and Apathy. | 
It is most fitting that Whitman’s last important paper relating 
to the leeches should have appeared in the “Festschrift zum sieben- 
zigsten Geburtstage’’ Leuckarts who had guided his early inter- 
est in the group. This memoir on ‘‘The Metamerism of Clep- 
sine,” is the culmination of Whitman’s work on metamerism. 
More than any previous work it is concerned with the nervous 
system and as an example of complete morphological analysis 
has few equals among papers dealing with invertebrates. The 
elements of the central neuromeres and peripheral nerves are cor- 
related one by one with such external features as annul, sensillae 
and eyes throughout the body and especially in the simpler somites 
at the two extremities. The presence in these terminal segments 
of every morphological element is determined and accounted for 
and the conclusion reached that complete homodynamy exists 
throughout. The earlier determination of twenty-six somites in 
the body of all leeches anterior to the caudal sucker, and of seven 
in the sucker was confirmed. 
Metamerism is traced to the extreme tip of the anterior end, 
where, however, there is a cephalic region in which the dorsal 
halves alone of the somites are represented and in which as a 
consequence, there is a delayed embryonic development. There 
is no non-metameric residuum at the anterior end and, although 
acknowledging that embryology furnishes some evidences of the 
presence of a rudimentary apical organ and remnants of a pair of 
head kidneys, Whitman denies that there is any element here 
other than, or added to, the first metamere. There is no pro- 
soma in the sense of Hatschek of an unpaired, non-metameric 
and premetameric region opposed to the segmented region begin- 
ning with the larval mouth. Whitman also contends that these 
facts confirm the opinion long held by himself in common with 
Leuckart and others that metamerism originated in multiplica- 
tion by fission. 
