134 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
same character as that already used for the ‘ first maxille.” The labial 
fundaments are appendages of the seventh somite in both Hexapods and 
Crustacea and are supplied by equivalent ganglia and nerves. In both 
groups each fundament is at first simple and secondarily develops a 
palpus, or exopodite. Moreover, the axis of the appendage is three- 
segmented, the segments in Crustacea corresponding to gula, mentum, 
and palpifers of generalized Hexapoda, the submentum being a secondary 
development. 
Hansen (93, p. 206) differs slightly: “ Das Submentum [Machilis] 
ist mit dem, bei den Gammarinen zusammengeschmolzenen ersten Gliede 
homolog, das Mentum mit dem bei den Hyperinen auch zusammenge- 
schmolzenen zweiten Gliede ; anf der Spitze des Mentums findet man ein 
Glied, das auf jeder Seite in vier Laden ausgeht, die, wie sich ziemlich 
deutlich zeigt, zwei Laden angehGren, die jede fiir sich gespalten ist, und 
diese halte ich (unter Anderem wegen eines Vergleiches mit Orthoptera 
und Amphipoda, kann aber keinen zwingenden Beweis von den Skelet- 
theilen fiihren) respectiv fiir eine Lade vom zweiten Gliede (die innerste 
gespaltene Lade) und fiir das dritte Glied des Labiums mit seiner ge- 
spaltetem Lade; der Palpus geht von der Aussenseite des dritten Gliedes 
aus.” 
Hansen should have taken into consideration the gula, and the fact 
that the submentum is probably not a primitive sclerite. 
The homologies between Hexapoda and Crustacea that I have defended 
are none the less valid if the total number of somites differs in the two 
classes, and they are sustained if the number is the same. In decapod 
Crustacea there are twenty-one somites, including the ocular segment. 
In generalized insects the number of abdominal segments varies. In the 
embryo of Lepisma, which shows marked affinities with Crustacea and 
Orthoptera, Heymons (97%) finds eleven abdominal somites. Add to 
these the thoracic segments and the seven which I have found in the 
Apterygote head; and the total, twenty-one, is the same as for decapod 
Crustacea. In embryos of many families of Orthoptera and Odonata 
just eleven abdominal segments are present. On the other hand, 
Heymons (’95°) has found twelve in certain genera of the same orders, 
and in Collembola the number varies greatly. In view of this variability 
within the limits of the same order, then, it is well not to emphasize the 
agreement between generalized insects and decapod Crustacea in the total 
number of somites. 
My conclusion regarding the labium, then, is that its development in 
Apterygota conforms to the Orthopteram type. In Anurida a labial pal- 
