224 Dr. C, F. J. Lachmann on the Organization of InfusoiHa. 



cavity destitute of proper walls (vacuole), which is sometimes 

 supposed to form the analogue of a heart*, and sometimes that 

 of an excretory t or respiratory J water-vascular system. In 

 order to be able to judge of these views, we must first of all 

 examine rather closely into the behaviour of the contractile space, 

 and for this purpose those Infusoria in which processes or 

 branches of the vesicle can be detected, appear to be particularly 

 important. 



Radiating branches of the contractile spaces were first disco- 

 vered by Ehrenberg in Paramecium Aurelia and some other In- 

 fusoria. When the contractile space is full and wide open, the 

 rays can only be observed as fine lines, or, when the light is not 

 good, are entirely imperceptible ; by the sudden contraction of 

 the space, however, they instantly swell into a pyriform com- 

 mencement close to the position of the contractile vesicle which 

 has disappeared. With favourable illumination, when the ani- 

 mals possess the proper degree of transparency, the rays may be 

 traced in Paramecium Aurelia across the half of the animal, and 

 we may sometimes perceive a bifurcation of one or other of them. 

 During the slow re-appearance of the contractile space, the rays 

 gradually decrease, and they have almost entirely disappeared, 

 or become reduced to fine lines, when the vesicle has attained 

 its full extension. These rays, as well as the contractile spaces, 

 lie, as in all Infusoria, close under the skin (^'cuticula^' of Cohn), 

 in the parenchyma of the body ("cortical layer" or "cell-mem- 

 brane" of Cohn). 



In many Vorticellce we also find processes going off from the 

 contractile vesicle (Ehrenberg even states that he has frequently 

 seen the contractile vesicle of CarcJiesium poli/jmium lobate or 

 almost radiate) ; of these I have been able to trace one particu- 

 larly, in V. nebulifera, campanula and Carchesium polypinum, up 

 to close beneath the skin of the ciliary disk; this, when seen 

 from above, exhibited a longish section (fig. 3 k). From this a 

 fine branch appears to run, on the upper wall of the vestibulum, 

 transversely across this to the other side ; at least I have seen a 

 thin process hanging down like a short curtain into the vesti- 

 bulum from the side turned towards the ciliary disk (in fig. 3 it 

 is represented by the broad dotted line which runs transversely 

 across the vestibulum from k), which swelled up when the above- 

 mentioned process became enlarged in consequence of the con- 

 traction of the vesicle. 



In Dendrosoma radians, Ehrbg., a fine vessel runs through 



* Wiegmann, Archiv, 1835, i. p. 12; Von Siebold, Vergl. Anat.^ 

 t Bergmann and Leuckart, Vergl. Anat. pp. 184 and 214. 

 j O. Schmidt, who, however, admits the existence of walls to the vesicle. 

 Froriep's Notizen, 1849, p. 5; Vergl. Anat. p. 220. 



