412 Mr. H. J. Carter on Dracunculus. 



forms : viz. seven in the salt water of the marshes and main 

 drain, of which six are males and females of three species re- 

 spectively ; two in the freshwater tanks, male and feaiale ; and 

 eight in the gelatinous Algfe on old walls, among which are six, 

 males and females of three species respectively. 



8. Of these it may be stated that the organology in all is the 

 same, and, so far as the alimentary canal goes, exactly like that 

 of the young Dracunculus. The generative organs and position 

 of the vulva are, in round terms, the same in all, — that is to 

 sav, the vulva is situated towards the middle of the body (fi'om 

 which departs in opposite directions the double tubular ovisac) ; 

 and the penis consists of two horny spicules approximated at 

 an acute angle just inside the anus, from whence it is exsertile. 

 In all, however, the variety in form of the head or tail, or both, 

 serves not only to distinguish the species, but frequently also 

 the sex of the species. In most (probably all) the oesophagus is 

 furnished with a rigid, sharp-pointed extremity, which is exser- 

 tile. Lastly, in all, the young are undistiuguishable from each 

 other, and closely allied in form to the young Dracunculus ; the 

 alteration in the head and tail not taking place before the deve- 

 lopment of the generative organs. 



Obsei'vations. — These facts show that the alimentary canal is 

 of the same construction in the young and old Dracunculus as 

 in the free microscopic Filarice above mentioned ; — that the ovi- 

 sac of the adult Dracunculus is as symmetrical in its two halves 

 as the double ovisac (so-called '^ uterus ^^) of the microscopic 

 species, but, from want of a vaginal outlet, is a uniform con- 

 tinuous tube, the diminished extremities of which resemble the 

 diminished extremities of the double ovisac, which are, in fact, 

 the ovaries ; — that the bursting forth of the ovisac, therefore, in 

 Dracunculus is an inevitable consequence, and has its parallel, 

 according to Van Beneden, in the bursting-forth of the "matrix^' 

 or so-called " uterus " rmder corresponding circumstances (that 

 is, when it becomes distended with ova) in the Cestoid Entozoa, 

 Taenia solium ; — that the oesophagus in Dracunculus being of the 

 same construction as that of the microscopic Filarice, is there- 

 fore, probably, provided with an exsertile point, which enables it 

 to bore its way through the tissues, after the manner of Cysti- 

 cercus, which is also similarly provided for this purpose; and 

 that this might enable the young of the microscopic species to 

 pass into the human body through the skin direct, or indirectly 

 through the ducts of the sudorific glands, the latter being much 

 larger in calibre (viz. l-1200th of an inch) than the young 

 Filariada, which ax-e frequently not wider than a human blood- 

 globule ; — that, from what we now know of Parthenogenesis, or 



