xl 



INTRODUCTION. 



it generally lies pendant from the inner side of the coxa, 

 and is longer in some species than in others. In the 

 genera Proto and Cajjrella, the penis seems to be 

 formed out of the anterior pairs of pleopoda, just as 

 is the case in the Brachyura, among the Stalk-eyed 

 Crustacea. These observations are further confirmed by 

 those of M. Eousel de Vauzeme on the genus Cyamus. 



In the Isopoda, these organs have been carefully worked 

 out by Siebold, Lereboullet, and SchobL In the genus 

 Ligia (Fig. 16), we have observed on each side three testes, 



consisting of long narrow 

 vesicles, thinning away to 

 exquisitely fine filamen- 

 tary prolongations. These 

 vesicles increase in dia- 

 meter as they approach 

 towards the efferent duct, 

 where they rapidly be- 

 come constricted before 

 uniting with the vas defe- 

 rens. These vesicles are 

 filled Avith seminal cells, 

 and are, we believe, the 

 true testes. M. Lere- 

 boullet, however, in his 

 researches on the Onis- 

 c'ulcEy^ states that he has 

 observed that each of 

 Fio. 16. these fusiform sacs has 



attached to its extremity other irregular sacs, which 

 he regards as the principal secreting organs, and con- 

 sequently the spermogenic glands or testicles. These 



* Mem. sur les Crustaces de la Fainile des Oloportides, par A. Lereboullet. 

 StrasLurgh, 1852. 



