162 NOTES AND MEMORANDA. 



of oxygen lost by this process, showed a loss of 5 per cent., and it 

 may therefore be said that the gas developed by these animals 

 does not contain less than 45 to 55 per cent, of oxygen, the residue 

 being considered nitrogen. 



It is easy to show the extreme importance of the action of light on 

 the life of these animals. Placed in darkness after a journey from 

 Roscoflf to Paris, all died in two, three, or four days, whilst others 

 exposed to diffused light decomposed carbonic acid and survived at 

 least two weeks. 



Treated with alcohol, the Planariae give a first solution of a 

 yellow colour, and after that, but somewhat less easily, a solution of 

 chlorophyll of a magnificent green. The residue of the bodies of the 

 animals, coagulated and discoloured by alcohol, boiled in water and 

 filtered, gives a clear solution which treated with iodized water has the 

 deep blue colour, which, disappearing by warming, proves the presence 

 of a considerable quantity of ordinary vegetable starch. 



Development and Metamorphoses of Tseniae. — Thirty years ago 

 Van Eeueden, Siebold, Leuckart, and Kiichenmeister established, by 

 experiments on carnivorous animals, not only that the vesicular worms 

 were imperfect forms of Ta^nife, but that it was indispensable that 

 the worms should be swallowed by an animal to bring them to the 

 perfect state. 



This view, while explaining the origin of the armed Tteniae of 

 carnivorous and some omnivorous animals, did not, however, explain 

 that of the unarmed Tsenite of herbivorous animals. The horse, ox, 

 sheep, &c., often have adult Tfenije, and yet they do not swallow any 

 organism capable of harbouring the scolecides of their Ttenife. 



M. P. Megnin thinks * he has discovered the key to the enigma 

 from an examination he made of some horses and rabbits. In these 

 animals, the Echinococci and Ci/sticerci, when they develop in the 

 adventitious cavities in immediate communication with the interior of 

 the intestine (cavities resulting from the enlargement of follicles or 

 glandules into which the hexacanthian embryos have introduced them- 

 selves), or even when they become free in the peritoneal cavity of the 

 wild rabbit, continue their metamorphoses on the spot, and arrive at the 

 adult state without quitting the organism into which they penetrated 

 as a microscoinc egg ( • 03 to -07 mm. in diameter) either with the 

 food or drink of the animals. In this case, however, they give rise to 

 an unai-med Tjeuia, whilst the same worm, if swallowed by a car- 

 nivorous or omnivorous animal, would become in its intestines an 

 armed Taenia, that is, provided with the hooks of the scolex from 

 which it originates, and which in the former cases it loses. 



Some unarmed and armed Tfeniae are therefore two adult and 

 parallel forms of the same worm, and the differences, often very great, 

 which they present (as in the Tcenia perfoliata of the horse and the 

 T. echinococcus or T. nana of the dog which originate from the same 

 worm), are due exclusively to the difterence of the habitations in 

 which their final metamorphoses are accomplished. 



* ' Comptes Rendus,' vol. Ixxxviii. (1879) p. 88. 



