130 MANUAL OF ANIMAL BIOLOGY 



latter consists of a linear series of four muscular compartments, 

 known as the ventricles, each of which possesses a pair of open- 

 ings, the ostia. The heart lies in a blood space, the pericardial 

 sinus, and the general relations between these structures are simi- 

 lar to those observed in the Grasshopper. The dorsal vessel, of 

 which the heart is a modified portion, continues posteriorly a short 

 distance from the heart and finally ends blindly in the abdomen. 

 Anteriorly this vessel passes into the head region where it gives off 

 the blood to the tissues. 



The course of the circulation of the blood is as follows. The 

 blood which has been received in the pericardial sinus passes into 

 the heart through the paired ostia. By the contraction of the 

 muscular walls the blood is driven anteriorly through the dorsal 

 vessel. It passes from the latter in the head region ; then moves 

 posteriorly and ventrally after bathing various body tissues, and 

 finally reaches the large ventral sinus, from whence it is carried 

 dorsally through special channels into the pericardial sinus. 



3. Excretory System 



The excretory system of the Bee consists of a considerable num- 

 ber of long filamentous tubules, all of which open into the intestine 

 near its anterior end. These are known as the malpighian 

 turules. The specialized cells in these tubules come into close 

 contact with the surrounding blood, and are able to take the 

 liquid waste products from the blood. These liquid excreta, 

 instead of leaving the body in a liquid form by special ducts, are 

 passed into the intestine. Thus the intestine serves not only as 

 an organ for the egestion of indigestible materials, but also as an 

 organ for the excretion of metabolic wastes. 



4. Reproductive System 



Male Reproductive Organs. The male reproductive organs 

 of the drones consist essentially of a pair of testes. These organs 

 are made up of a great number of fine, coiled tubes, the spermatic 

 turules, in which the sperm develop. In a testis, the spermatic 

 tubules all connect at one end with a much larger coiled duct, the 

 vas deferens, and this in turn empties into a still larger uncoiled 

 portion, the seminal vesicle. Each seminal vesicle opens into a 

 glandular structure, designated as the accessory gland. The 

 glands from each side unite, and from this union the common 



