1884.) Anatomy and Physiology of the Family Nepide. 357 
larve of Belostoma, Perthostoma and Ranatra in flat glass boxes, 
and, with the microscope, have studied the heart, and traced the 
circulation through the transparent integument. 
The heart here described is from dissections of Belostoma. It 
consists of a long tube extending from the sixth abdominal seg- 
_ ment to the supra-cesophageal ganglion. In the abdomen, it is 
divided into chambers, and this abdominal portion is considered 
the heart proper, and the anterior tubular portion, the aorta. 
There are five chambers in the abdomen of the adult, with affer- 
ent openings on each side, called by some auriculo-ventricular 
apertures. At the beginning of the sixth abdominal segment, 
the heart is attached to the integument by means of muscles. 
(Fig. 4.) 
The first pair of afferent openings are thus thrown into the fifth 
abdominal segment, and the three following segments have one 
pair each, making a total of four pairs. These openings are 
guarded by valves, the action of which will be considered later. 
These apertures are all anterior to the middle of the body segment 
inwhich they are situated. In the larve of Belostoma, I have often 
i one of these auriculo-ventricular openings in the sixth 
r inal segment, and muscular attachments behind it in the 
anal prolongation. It is my belief that this additional chamber is 
dropped in the adult form, since I find it in none of my dissec- 
tions, It is a matter of great difficulty to be sure, whether one of 
these chambers may not have escaped notice. According to my 
he ions, however, there are five chambers in the adult 
stoma and six in the larva. At the junction of the thorax 
id the abdomen, the heart bends downward as it extends for- 
` passing under the large muscles of the thorax. 
The triangular Muscles of the Heart —The heart is attached to 
Pie integument in the abdomen, by a number of triangular mus- 
With their apices pointing outward. I have counted eight 
of these attachments in the adult Belostoma. They are 
$d opposite each auriculo-ventricular orifice, and continue 
anteriorly, and posteriorly, beyond these openings. At the 
Naas 1e fibers composing the triangular muscles are closely 
“© into a sort of ligament. These fibers diverge laterally as 
approach the heart, and also divide into two sheets, one pass- 
om e and the other below the heart. Thus a triangular cav- 
left on each side of the heart, which is called the pericardial 
Ai: 
