254 REPORT — 1851. 



extent, of the general circulation ; since opposite to each membranous bag a 

 portion of the fluid contained in the lateral vessel is given oflp through the 

 muscular tube, which thus resembles a pulmonary heart, and after being dis- 

 tributed over the walls of the respiratory sacculi, and in this manner exposed 

 to the influence of oxygen, the blood returns into the general circulation*." 

 While the description of M. Duges, just cited, does not very untruly represent 

 the mere anatomical characters of the parts to which it relates, the error of 

 interpretation involved in his views, the fact that he saw in the wondrous 

 structure displayed by these parts a fantastic mechanism for respiration, is 

 as extraordinary as any false conception ever known in the history of compa- 

 rative anatomy. 



It will subsequently be found that his marvellous muscular fusiform hearts 

 for circulating the blood over the so-called respiratory sacculi, are true and 

 unquestionable ovarian utricles, proved to be such by the discovery in them 

 of veritable ova. 



The respiratory sacculus (of Duges), scrutinized through the searching 

 eye of the modern microscope, resolves itself into a simple vesicle pendent 

 to the ovario-uterine system ; and the extraordinary blood-vessels of M. 

 Duges appear only as tubes connected with these two parts of the female ap- 

 paratus. 



The author will now proceed to describe the whole reproductive system of 

 the Leech as deciphered by his own investigations. Having once seized the 

 true key to the interpretation of the physiological meaning of the several 

 component elements of this system, the mere anatomical process of deter- 

 mining its limits became easy of execution. In the ordinary medicinal leech 

 the whole apparatus presents the same characters in every individual. The 

 leech is therefore monoecious or hermaphrodite. The union of two indivi- 

 duals is however essential to impregnation. This rule may be stated to be 

 applicable to the great majority, if not absolutely to all, of the Annelida. 

 The masculine and feminine moieties of the system bear to each other a pro- 

 portion of equality. The testicular bodies and ovario-uterine organules are 

 nearly equal in number, the latter slightly preponderating over the former. 



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

 disposed at short distances in a longitudinal series on c Ither side of the ventral 

 median line of the body (Plate VIII. fig. 65 a, a, a, &c.). When forcibly 

 compressed, a white fluid exudes, which under the microscope is found to 

 consist of nothing but sperm-cells (C.) in various stages of evolution. To 

 each of these testicular bodies two (fig. 65 erf, cd, &c.) minute threads are 

 attached. The larger and more obvious of these threads (fig. 65 c) 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-cells, a true male secretion. The longitudinal 

 tube (f) is common to all the testicular bodies ; it begins at the most pos- 

 teriorly situated of these bodies, and ends in that most anteriorly placed, 

 median and azygos (J), to which the intromittent 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 and 

 much smaller one (d, d, &c.) may be detected on minute dissection running 

 directly outwards, crossing underneath the large longitudinal duct (/,/) and 

 becoming united (as a.tff,ff, g) to the base of the ovarian utricle. Traced in 

 the direction of the head, the longitudinal duct is seen to enter into a glan- 

 dular body (h)y which in size is considerably greater than the testes situated 

 * Op. cit, p. 198, 



