Secreting Organs in Nematoidea. 47 



two tenable hypotheses regarding them. They have evidently 

 nothing to do with the reproductive apparatus, as they are 

 equally present in both males and females, and seem to have no 

 connexion in either with the sexual organs. They might, how- 

 ever, be either secreting glands or intestinal caeca. The latter 

 hypothesis I should be inclined to regard as very improbable j 

 for though cseca are described and figured by Leidy, of Phila- 

 delphia, and others, as I have before mentioned, yet in all those 

 species in which they occur we find them placed much higher 

 in the alimentary canal, often at the point where the stomach 

 or intestine joins the oesophagus : they are usually single or un- 

 symmetrical, always hollow; and though often communicating 

 with the intestine by a narrow neck, yet rarely or never is that 

 structure so suddenly attenuated and duct-like as is constantly 

 the case in these secreting organs in Ascaris dactyluris. We 

 are thus led to adopt the last hypothesis, that they are special 

 glandular structures — an opinion which, I think, is supported by 

 their numbers, by their thick, solid, granular walls, by their long 

 ducts, when present, and by their invariably low position with re- 

 gard to the alimentary canal. This latter point is also of much 

 importance in relation to the function fulfilled by these bodies, if 

 glandular; for as their secretion would be poured into the lowest 

 portion of the rectum, it could not be to any extent excrementi- 

 tious in its nature, but must be directly evacuated before absorp- 

 tion could take place ; so we may regard these organs as a means 

 of evolving efiete matter from the system : mayhap they might be 

 among the earliest examples of a renal apparatus in the animal 

 kingdom ; and if so, certainly they are the first examples of such 

 having been found in the Entozoa. Indeed, as a general rule 

 among the lower departments of animal life, the appearances of 

 renal organs are more or less equivocal : even in the Insecta the 

 Malpighian tubes (by far the most distinct urinary apparatus in 

 the Articulata) were often mistaken for hepatic organs, until 

 Brugnatelli and Wurtzer proved that these canals contained 

 urate of ammonia in the Silkworm, as Meckel afterwards demon- 

 strated in Mefo/onMa(Archiv fur Physiologic, 1816, 1818, 1826). 

 In Myriapoda the same tubular structure obtains with tolerable 

 distinctness ; and in Crustacea we have the urinary system re- 

 presented by the tubes traced by Milne-Edwards in Maia, by 

 Duvernoy in Portumnus, and by Meckel in Palamon and others. 

 Usually these are cseca, which open sometimes into the pylorus 

 but occasionally into the rectum. No representative organ has 

 been, to my knowledge, described in Annelida. In Echino- 

 dermata Jager has referred to the slightly branching sinuous 

 tubes of Holothuridse as being renal in their nature ; but Miiller, 

 who describes these structures under the name of the Cuvierian 



