Ifi'scellaneoHs. 67 



blood in the various cephalothoracic lacuntie may be slightly 

 variable. 



At the point where it divides to give off the pedal arteries each 

 trunk of the aorta piniits a short branch towards the sternal face ; 

 the two sanguineous currents thus formed encircle the sucking 

 stomach, and, uniting forthwith, travel below the oesophagus and 

 come into view beneatli the integument, pouring numerous globules 

 into the median sternal lacuna. This is probably the first of the 

 anastomoses described by M. Schneider, that which gives off the 

 suhcesojihageal vessel. 



Though the abdomen is but slightly transparent the heart is 

 generally quite visible, as also the two anterior pairs of its orifices 

 {pylocardia of Schiieider). The posterior pair is usually very diffi- 

 cult to observe. The blood which returns from the lungs into the 

 pericardium enters the heart partly by the anterior and partly by 

 the median orifices. In the posterior portion of the pericardium 

 the globules circulate /Voh? behind forwards, to arrive at the median 

 and posterior orifices. The blood which, penetrating into the ante- 

 rior portion of the heart, is not sent into the aorta, circulates in 

 this organ from in front haclcivurds. I have nevertheless once seen 

 in the anterior region of the heart the sanguineous current produced 

 from, behind forwards, because the greater portion of the blood 

 returning from the lung gained the median instead of the anterior 

 orifices of the heart. 



I have not been able to directly observe globules issuing from the 

 heart by the lateral arteries of M. Schneider ; but in young speci- 

 mens of Heliojjhanus I have succeeded in seeing in the posterior 

 portion of the body a sanguineous current recede from the heart 

 and branch off to lose itself in the liver. In young individuals of 

 Dictyna and Chiracanthiiim I have perceived at the sides of the 

 abdomen a current of globules proceeding towards the ventral face, 

 which probably belonged to one of these arteries. 



The blood which escapes from the posterior portion of the heart 

 passes into the pygidial lacuna, which surrounds the anus and the 

 spinnerets. It divides into two currents, which reach the ventral 

 face ; a few globules separate from the rest to circulate in the 

 spinnerets before rejoining the common route. These two currents 

 flow forwards, following the longitudinal ventral muscles, and 

 mingle with those which have come from the cephalothorax, in the 

 interval which separates the two lungs. The globules disappear 

 behind the respiratory lamellae, to reappear on the outer side and 

 be swallowed up in eddies by the corresponding pulmonary vein, 

 which conducts them to the pericardium opposite the anterior 

 orifices. 



The whole of the blood which reaches the heart has not previously 

 passed through the lungs. As a matter of fact globules may be 

 observed at the sides of the abdomen, which, issuing probably from 

 the mass of the liver, appear beneath the integument and there 

 circulate until th^y reach the pericardium, whence they penetrate 



