REPORT ON THE PYCN OGONIDA. 127 
In Nymphon the number of lateral cxca of the alimentary canal is five pairs. Of 
these the first pair is very wide and directed forwards. At the base of the proboscis 
it divides into two branches. One (the larger one) is directed upwards and forwards, 
and penetrates the mandibles ; the other one enters the proboscis and divides, in some 
species (Nymphon brachyrhynchus, e.g.), again into two branches. These extend in some 
species farther than in others, but I never observed them beyond the hindermost half of 
its length. : 
The groups of comparatively large cells with very thin walls and distinct nuclei, each 
of them containing, as a rule, one (sometimes more) strongly refracting granule probably 
have also some relation to nutritive functions. These I observed in ymphon, Phoxi- 
chilidium pilosum, and in Colossendeis, collected in large groups sometimes about fifty 
in number. They seem not to be limited to any particular part of the body, but I 
found thém always in the neighbourhood of the muscles, between the connective tissue, 
where fibrous threads keep them in place. I feel inclined to consider them as analogous 
to the fat-cells of most Arthropods. I figure a group of them in Pl. XXI. fig. ..9) 
5. The Circulatory Apparatus.—The somatic cavity is divided into distinct compart- 
ments, by means of sheets and bands of fibrous tissue. One of these, placed between the 
dorsal wall of the intestine and the dorsal integument of the body, is furnished with 
contractile walls, and has the function and the structure of a heart: In Colossendeis this 
heart is not surrounded by a pericardial sinus (PI. XXI. fig. 14, h, Pl. XVII. fig. 1). The 
blood, entering the apertures of the heart, comes directly from one of the longitudinal 
compartments into which the somatic cavity is divided. The contractile walls of the heart 
do not enclose it on all sides ; for on the dorsal side a part of the integument is used to 
form the dorsal wall of the heart. The contractility of these walls is due to the presence 
of muscles, which run in a transverse direction and are not striated. Along both sides 
of the heart these muscles are inserted into the dorsal integument of the body. As 
to their structure, I observed their fibres to be extremely thin and slender. When 
studying them with a strong lens (e.g., 11, Immersion of Hartnack) I observed that they 
exhibit parallel edges only for a certain distance ; for this pagallelism almost imperceptibly 
passes over into an extremely feeble swelling of the fibre, in the interior of which a 
long nucleus with a distinct nucleolus is observed. 
The heart of the Pycnogonids, as a rule,’ is furnished with three pairs of apertures. 
‘ In one specimen of Nymphon brachyrhynchus I observed that one of the branches penetrating the proboscis 
divided again, so that in the same section, through about the middle of the proboscis, five sections of intestinal ceca 
were observed. This I consider of no importance at all. It only proves, I believe, that it is almost dangerous to 
attribute any fundamental value to the number of pairs of cca arising from the intestine. In a large specimen of 
-Pycnogonum litorale a section of the fourth joint of the leg shows two sections of ceca in the same joint: the cecum 
has given off a branch. Consequently I believe that the number of these branches depends in general upon the capacity 
of the different appendages. In Nymphon and Colossendeis no ceca are observed entering the palpi and the ovigerous 
legs, only because the capacity of these extremitiés does not allow of it. 
“2 Not always. Pallene brevirostris, Johnston, ¢.g., has only two of these. 
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