No. 2.] ANURIDA MARITIMA. 279 
opes of higher tracheates, are connected strictly with terrestrial 
forms and are one of the necessary adaptations to the exigen- 
cies of land life. Whether or not the ancestors of Anurida 
ever possessed such structures and have since lost them in 
consequence of acquired semi-aquatic life cannot be settled, 
but it is interesting to speculate on the possibilities of Anurida 
being a simple form and still retaining a semi-aquatic mode of 
life and showing a few transitional characters. 
Notes on Other Points of Interest. 
Nervous System. —No detailed observations were made on 
the development of the central nervous system, but a few points 
of correspondence with other forms were noted. The brain and 
ventral cord both arise in the same way as that described by 
Wheeler ('93) for Xiphidium, — by the proliferation from single 
ectoderm cells until rows of nerve cells arise. Proliferation is 
in the direction of the dorso-ventral axis of the embryo, and is 
restricted to certain places in the segments; subsequently, 
these primitive ganglia are united to form the ventral cord. 
Ultimately the six abdominal ganglia are fused to form a mass. 
The brain portion may be readily seen to have the three suc- 
cessive segments, protocerebrum, deutocerebrum, and trito- 
cerebrum. The optic lobes form a large part of the young 
protocerebrum. Above the stomodeal invagination soon arose 
by proliferation from the hinder end a cord similar in structure 
to the ectoderm of the invagination that after reaching a con- 
siderable length remains unchanged, but a prominent character 
even in late embryonic life. It is entirely missing in the young 
animal and nothing remains to suggest its former presence. 
From the method of origin it is concluded that this is a trace 
of a sympathetic system, this being the history of this system 
in other insects; but since the adult seems to lack a sympa- 
thetic system, its degeneration is to be expected. Pauropus, 
that low, degenerate myriapod, also lacks a sympathetic system. 
These are mere notes on the general features of the nervous 
system, and a more complete study will be reserved for a 
future occasion. 
