REPORT ON THE PYCNOGONIDA. Utlys 
Bell, e.g., the commissures between the third and fourth ganglia are the longest; in 
Nymphon brachyrhynchus, however, those between the second and third are the longest. 
In Colossendets and in Phoxichilidium pilosum the relative length is the same as in 
Nymphon robustum. Tn all the species and genera I observed the commissures between 
the last two thoracic ganglia to be shorter, often much shorter, than those between the 
preceding ganglia. The nerves which arise from these ganglia in Colossendeis immediately 
divide into two branches, whereas in Nymphon they only separate after having reached 
the middle of the lateral process at the end of which the leg isinserted. In Phowi- 
chilidium pilosum they again divide immediately after leaving the ganglion. The last 
ganglion has a truncated form; in most of the genera I studied I observed at least a 
trace of the presence of the small accessory ganglia (abdominal ganglia) which Dohrn 
observed in Phowichilus, and which I found beautifully developed in a young specimen 
of Colossendeis proboscidea. 
Close to the hinder margin of the ganglion two small excrescences arise from its 
dorsal surface. They are separated from one another by a small space, and as they unite 
again at a short distance from the ganglion a round area is left between them. Ina 
full-grown specimen of the same species only a single excrescence was observed, arising 
from the hinder margin, and I observed it of the same form in Colossendeis megalonyx 
and also in C. leptorhynchus. I did not observe it in Nymphon; but in the species 
of that genus which I studied (N. strémii and N. robustwm) I always saw two distinct 
medullary nuclei in the interior of the ganglion placed close to its hinder margin, behind 
the large medullary masses from which the nerves for the hindmost pair of legs arise. 
According to Dohrn, the nerves which arise from this ganglion are two in number, 
besides the two stout nerves for the hindmost pair of legs. It is extremely difficult to 
avoid confounding threads of connective tissue, arising from the neurilemma that surrounds 
this ganglion with nerves. I have, however, distinctly observed that often four different 
nerves branch off from the ganglion ; in Colossendeis proboscidea, e.g., two smaller ones 
are given off more in the middle from the dorsal excrescence, and two stouter ones 
leave the ganglion nearer to the nerves which innervate the fourth pair of legs. Two 
pairs of nerves arising from the hinder surface are also present in C. leptorhynchus; but, 
strange enough, only one pair (that arising from the excrescence in the middle of the 
hinder margin) in Colossendeis megalonyx. In the genus Nymphon the two nerves which 
arise from the ganglion leave it as one single nerve, and only afterwards divide into two 
branches. The same difficulty is experienced in ascertaining the presence of nerves 
branching from the commissures which unite the different thoracic ganglia. These are 
present, however, in all the genera, and even in all the species I studied. As a rule, they 
leave the commissures much nearer to the preceding than to the following ganglion, but 
often also nearly in the middle of the commissures; between the second and third, 
between the third and fourth, and between the fourth and fifth thoracic ganglion, 
