Miscellaneous. 73 



only with that portion of the circulatory apparatus which is contaiuecl 

 in the abdomen, that is to say with the heart and the vessels which 

 open into or issue from it. 



The heart of the mason Mi/gah greatly resembles that of the rest 

 of the spiders. Enveloped by a pericardium it is situated in the 

 dorsal portion of the abdomen, immediately beneath the integument. 

 Its anterior region is attenuated to form the aorta, which penetrates 

 into the peduncle and passes on to ramify within the cephalothorax. 

 Its posterior portion exhibits a corresponding diminution in size, and 

 then terminates with a bifurcation. In transverse section it is not 

 circular, but shows an augle in its lower part, since the heart is as 

 it were carinate on its inferior face. Four pairs of lateral 

 eminences are to be observed upon this organ. The anterior pair, 

 which correspond to the curvature of the heart, are but slightly 

 marked ; the following pair, which I shall call the intermediate ones, 

 are much more prominent, as are also the third {median) ; finally 

 the posterior pair, situated near the extremity of the heart, are much 

 less pronounced. Each of these eight eminences is perforated by an 

 aperture, forming a communication between the pericardiac cavity 

 and the interior of the heart. There are accordingly four pairs of these 

 apertures, while the Araneida Dipneumones only possess three pairs, 

 and less in a few very rare cases. The number four has, moreover, 

 been stated by M. Blanchard for Mi/r/ale Blondii. The anterior 

 apertures are placed at the sides of the heart ; the intermediate ones 

 are a little further advanced towards the dorsal face ; and, lastly, the 

 median and posterior pairs are almost entirely dorsal, and in these 

 cases the two apertures of the same pair are separated one from 

 another, in the median line, only by a somewhat narrow strip of 

 tissue. Like the corresponding eminences, the intermediate and 

 median apertures are much more developed than the anterior, and 

 above all than the posterior pair. The two edges of each aperture 

 are constituted by powerful bundles of muscular fibres, which 

 sharply define them. 



According to il. Blanchard, the heart of Mjjfjale Blondii is divided 

 into five chambers. In the mason Mi/ya/e this division into 

 chambers does not exist, any more, in fact, than in the Araneida 

 Dipneumones. On examining the interior of the heart, we observe 

 that the two lips of each aperture are turned back in such a way 

 as to make a noticeable projection on the inside of the heart when 

 they are applied together. The internal angles of the two apertures 

 of the same ])air arc only united together, on the interior of the 

 organ, by a slightly projecting raphe, which is produced by the 

 muscles which encircle these orifices ; on the floor of the heart a 

 similar seam is even much less distinct. The arrangement here 

 described is that of tlie intermediate and median apertures ; it is 

 even much less pronounced in the case of the anterior and posterior 

 ones. Neither do we find the vahndar fufds, which, according to 

 Duges, should conceal tlie origins of the vessels. The heart therefore 

 forms only a single chamber, exhibiting four enlargements. 



As regards the vessels, Duges confines himself to stating that 



Ann. (Si) Mag. N. Ili'st. Ser. 6. Vol. xii. 6 



