BRITISH MARINE TURBELLARTA. 439 



fertilisation is accomplished, the term sperm otheca is a con- 

 venient equivalent for " bursa seminalis," used by v. GrafiF. 

 In many cases (e. g. Vorticidae) two organs are present, one of 

 which receives the male products of another individual, and 

 then passes it on to the second, from which fertilisation takes 

 place. I retain the term bursa copulatrix for the former 

 muscular structure, and receptaculum serainis for the 

 latter. While the ova are being duly fertilised, provided with 

 food-yolk, and surrounded by an egg-capsule, they are usually 

 retained within the body of the parent during, and usually 

 also a short time after, these changes. Consequently a cer- 

 tain amount of development is passed through. To the 

 region in which this takes place the term uterus may be 

 applied. 



The testes offer no difficulties of terminology. Vasa 

 efferentia may be applied to cases such as Polyclads, where 

 a fine duct passes from each testis-follicle, and vasa de- 

 ferentia to the paired canals formed by their union. These 

 canals usually open into a vesicula seminalis. Accessory 

 male glands are very commonly present, and possess fairly 

 uniform histological characters. Hence the terms granule- 

 gland, granule-duct, vesicula granulorum. The duct 

 through which the male products reach the exterior is the 

 ductus ejaculatorius, and any chitinous investment round 

 it may be called a copulatory organ. 



As regards the authors' names appended to the species, I 

 have endeavoured to follow the British Association rules. 

 Von Graff, in his ' Monograph,' has employed the name of 

 that author who first used the definitive combination of genus 

 and species. Thus Vortex balticus, M. S. Schultze, becomes 

 Provortex balticus, v. Graff, whereas 1 write it Provortex 

 balticus (M. S. Schultze). 



The terminations of generic names have not hitherto been 

 formed in an uniform way. Von Graff changed the termina- 

 tions of all the older generic names, such as Acmostomum, 

 to Acmostoma, whereas Lang retains the -um form. In the 

 present paper I have followed these authors. It would, how- 

 ever, seem advisable in the future to adopt either one termina- 



