M. Valenciennes on the Gorgonidse. 177 



chamber is smaller than the middle, and this than the anterior 

 one. The latter is very considerably enlarged immediately be- 

 hind the above-mentioned tubercle,, and is no doubt in free 

 communication with the cavity of the body or the interstices 

 {lacunce) between the organs, and this is very probably the case 

 also with the hinder chamber. In the bottom of each notch 

 there is an opening for the entrance of the returning blood, so 

 that there are four such apertures, arranged in pairs. From 

 this description it is evident that the heart of the Pycnogonidae 

 agrees essentially in form and structure with that of the higher 

 Arachnida. 



The circulation goes on pretty rapidly in a distinctly marked 

 course, and if the nutritive fluid contains a sufficient quantity 

 of blood-corpuscles, may be easily observed. The chambers of 

 the heart contract simultaneously. At each diastole, the blood 

 returning from the organs is taken up by the heart through the 

 four lateral openings and driven forwards at each systole. In 

 this manner a small portion of the blood reaches the proboscis, 

 whilst the greater part takes its course in the form of a consi- 

 derable stream towards the abdomen. From this principal cur- 

 rent, lateral streams are given off to the legs ; these pass down 

 one side of the respective legs and up the other, so as to return 

 at last to the heart. 



In conclusion I must remark, that Van Beneden has already 

 observed a regular circulation of the blood in the legs of Nym- 

 phon^. He could not discover the heart, and according to him, 

 the impulse is given to this current of blood in the extremities 

 by a peculiar, rhythmically contractile membrane, situated within 

 the base of the legs. But as it is now certain that the blood 

 circulates in all parts of the body by the action of the heart 

 alone, we may very justly doubt the existence of any such ar- 

 rangement as this in the legs of the Pycnogonidae. 



EXPLANATION OF PLATE VII. 



Fig. 7. Sketch of the heart of Phoxichilus. The numbers 1-4 indicate 

 the several thoracic segments ; a, proboscis ; b, abdomen ; c, the 

 four eyes ; d, d, d, d, the legs ; e, e, the stomach with its lateral 

 caeca ; /, intestine ; g, the anterior, h, the middle, and i, the 

 hinder chamber of the heart ; A;, h, the constrictions of the heart. 



^^\.— Abstract of a Monograph of the Family Gorgonidae. 

 By M. Valenciennes. 



M. Milne-Edwards has shown that the animals of the class 

 of Polypes belong to two great orders. One of these, called 

 Anthozoa (Zoanthaires), includes those animals which more or 

 * Froriep's Notizen, xxxvii. p. 72- 



