28 THE ANATOMY OF THE LEECH. 



a branch -which is distributed upon the respiratory sacculus ; and 

 there is another very flexuous vascular loop derived from the lateral 

 vessel itself, which terminates by ramifying upon the vesicle in a sim- 

 ilar manuer. The -walls of the loop are extremely thick and liig'nly 

 irritable; but on tearing it across, the internal cavity or canal by 

 -which it is perforated is seen to be of comparatively small diameter* 

 so that we are not surprised that, although such appendages to res- 

 piratory sacs were detected and well delineated, their nature was 

 unknown, and they were supposed to be glandular bodies appropriated 

 to some undiscovered use. 



The female sexual organs are thus described by the same observer : 

 " The ovigerous, or female sexual organs, are more simple in their 

 structure than those which constitute the male system ; they open 

 externally by a small orifice situated immediately behind the aper- 

 ture from which the penis is protruded, the two openings being 

 separated by the intervention of about five of the ventral rings of the 

 body. The vulva or external canal leads into a pear-shaped mem. 

 branous bag which is usually, but improperly, named the uterus. 

 Appended to the bottom of this organ is a convoluted canal which 

 communicates with two round whitish bodies ; these are the ovaria. 

 This description, therefore at once makes a vast disproportion between 

 the male organs and the female, giving to the latter an unknown pre- 

 ponderance over the former ; for all anatomists are agreed as to the phy- 

 siological import of the rows of glandular bodies known as the testes. 

 Now we will contrast with the above the statements and observation 3 

 of Dr. Williams. 



The testes are observed under the character of small white granular bodies, dis- 

 posed at short distances in a longitudinal series on either side of the ventral median 

 line of the body. When forcibly compressed, a white fluid exudes, which under 

 the micioscopo is found to consist of nothing but sperm-cells, in various stages of 

 evolution. To each of these testicular bodies two minute threads are attached. 

 The larger and more obvious of these threads extends outwards at right angles 

 with the median line, and joins a considerable chord running parallel with the 

 median line. Examined in section, both the transverse threads and longitudinal 

 chord prove to be tubes filled with fluid thickly charged with sperm-celis, a true 

 male secretion. The longitudinal tube is common to all the testicular bodies; it 

 begins at the most posteriorly situated of these bodies, and ends in that most ante- 

 riorly placed, median and azygos, to which the intromitteut organ is appended; 

 meeting at this mesial organ the corresponding duct of the opposite side. In 

 addition to the tubulus just described as proceeding from the testes, another much 

 smaller one may be detected on minute dissection running directly outwards, 

 crossing underneath the large longitudinal duct and becoming united to the base 

 of the ovarian utricle. Traced in the direction of the head, the longitudinal duct is 

 seen to enter into a glandular body, which in size is considerably greater than the 



