EEPORT ON THE PYCNOGONIDA. 127 



In Nymjylion, the uumber of lateral casca of the alimentary canal is five pairs. Of 

 these the first j)air 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 lengjth.' 



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 Nymiilion, Phoxi- 

 chiliclium 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 l^ody, Ijut I 

 found them 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 PI. 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, li, PI. 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 parallelism 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 hrachyrhynchiis I observed that one of the branches penetrating the proboscis 

 lUvided again, so that in the same section, through about the middle of the proboscis, five sections of intestinal cfeca 

 were observed. This I consider of no importance at all. It only jjroves, I believe, that it is almost dangerous to 

 attribute any fundamental value to the number of pairs of caeca arising from the intestine. In a large specimen of 

 Pycnogonum litorale a section of the fourth joint of the leg shows two sections of caeca in the same joint : the csecum 

 has given off a branch. ConBequently I believe that the number of these branches depends in general upon the capacity 

 of the ditferent appendages. In Nymphon and Colossendeis no Cceca are observed entering the palpi and the ovigerous 

 legs, only because the capacity of these extremities does not allow of it. 



^ Not always. Fallene brevirostris, Johnston, e.g., has only two of these. 



