430 GENERAL niSTORY OF THE INFUSORIA. 



of the ventral region, and is attached to the head-mass behind the jaw- 

 cushion. The middle part of each thread is wrinkled into a large plexus of 

 four or five pairs of doublings, laid with some regularity ; on this plexus are 

 placed four tremulous tags, directed inwards, making eight in all. jN'one are 

 visible on any other part of the threads. The presence of these organs, as 

 well as of the contractile bladder, in the female, shows that these are not con- 

 nected with impregnation. 



From the above extract it appears that Mr. Gosse believes that the 

 " tortuous threads " of the apparatus have a glandular ofiice ; and though he 

 so far countenances the hypothesis of Ehrenberg, nevertheless pronounces 

 against their sexual nature. 



Dujardin expresses an opinion that the contractile vesicle is a respiratory 

 organ, and that the water freely penetrates into the interior of the body to 

 bathe the vibratile organs, as the variability of volume of the animals proves. 



Leydig has very elaborately described the structures in question, and their 

 several modifications. We feel justified in submitting an analysis of his 

 researches, even at the risk of some repetition : — 



" The canal of the respiratory apparatus extends along each side of the body. 

 Generally there is a single canal on each side, much contorted in its course, 

 and forming actual coils or plexuses, e. g. in Steplianoceros, Bracliioncea, 

 Lacinularia, Euchlanidota, and many Notommatce. Two canals, which 

 coalesce at either end, are seen in Notommata Myrmeleo, N. SiehoJdii, N. 

 Syrinx, N. clavidata, and N. AncjUca. The canals have a thick cellular wall, 

 and their cavity is clear and well defined. They are not solid cords, as Perty 

 and others affirm. The cellular walls may be much thickened, and contain, 

 besides the usual fine granular contents, many fat-particles, as seen in Ste- 

 phanoceros, Notommata centrura, and in Lacinidaria. In the first-named, 

 indeed, the deposit of fat is so great that the coils of the respii'atory canal 

 near the head rather resemble a collection of fat- vesicles (XXXVII. 1 t). I 

 have not been able to discover any anastomoses between the canals of opposite 

 sides, as Huxley represents in Lacinidaria.^^ 



In many Eotatoria, particularly in small species, such details of structure 

 escape our powers of observation, and the canals described are invisible, as, for 

 example, in Floscidaria, Polyartlira, ^n^Ascomorpha; a more close and search- 

 ing inquiiy may, however, reveal them, particularly where the contractile sac 

 shows itself. Indeed, Perty has detected the tubes in Ascomorpha Helvetica. 



" The vibratile or cihated tags are processes of the respiratory canal (XL. 

 5). They are constructed after two tj^^es, which do not concur in the same 

 animal, but are found as peculiarities of different genera. In one ij^Q the 

 process is of equal width and cylindrical throughout, as in Notommata 

 Myrmeleo (XXXYIL 29 e, 32 h) ; in the other, the extremities are dilated 

 and a trumpet- shaped figure assumed, as in Notommata centrura (XXXYIII. 

 26 e), Euchlanis triquetra, and in Eospliora Najas. 



^' In Lacinularia I have been unable to satisfy myself if these processes of 

 the respiratory canal discharge themselves freely into the abdominal cavity. 

 Huxley states that they have bhnd extremities ; but I regard it as still an 

 open question, for in other species, for example in Notommata Sieboldii and 

 N. centrura, it can be most satisfactorily made out that they open freely into 

 the cavity of the body. 



" Vibratile haii'S (cilia) project from their free end and in the trumpet- 

 shaped processes ; the direction of the ciliary motion is e\ddently inward. 



'* The number of the vibratile organs varies much in different species : 

 usually there are but from 4 to 8 or 10, distributed at unequal distances along 

 the respiratory tube ; but in some animals, e. r/. in Noto7nmata Copeus, N. 



