434 
PAUL PELSENEER. 
r a is found in each cord ; then come, in succession, the 
mandibular and maxillary ganglia, the maxillipedal nerves, 
which are observed coming out of the cord like the antennary 
nerves, and the ganglion of the first thoracic foot. 
Professor Ray Lankester has already pointed out the peculiar 
disposition of this nervous system, and when I came, during 
the winter of 1884 to 1885, to w r ork under his direction, he 
urged me to study the subject. I take the opportunity to 
thank him here for the courteousness with which he received 
me in his laboratory, and for the good advice which he gave 
me during the time I spent in London. 
In the course of my researches I have tried to elucidate the 
different points to which Professor Ray Lankester had drawn 
the attention of zoologists ; they are the following : 
I. The antennary nerves issue from the abdominal cord 
between tbe brain and the elongated swelling. Does this 
swelling arise from the fusion of the first and 
second ganglia? Or have the ganglia of these two 
appendages entirely disappeared, like the maxil- 
lipedes’ ganglion, instead of fusing with others? 
II. A pair of postoesophageal ganglia (the elon- 
gated swellings) exist anteriorly to the mandiblu- 
lar ganglia, which are generally considered as the 
first ganglia of the abdominal cord. 
III. Among superior Crustacea the brain gives birth to the 
nerves of the two pairs of antennae. If we consider the nervous 
system of Crustacea as finally formed by two more or less 
distant lateral cords upon which is found a ganglion for every 
appendage, and a special cerebral ganglion-pair in which the 
two cords unite in front of the mouth, then the brain of supe- 
length of 2'3 mill., the second of 0’9 mill. It is generally difficult to notice 
the second pair when one does not know where it is situated. Its position 
is not exactly shown by Zaddach (* de Apodis cancriformis anatomia et 
historia evolutionis,’ pi. i, fig. 5, b) ; its insertion, in comparison with the first, 
is external, not internal. 
