Dr. C. F. S. Lachmann on the 07'ganization of Infusoria. 227 



nor have I ever been able, in other Infusoria, to confirm 

 O. Schmidt^s assertion* that the contractile vesicle opens exter- 

 nally. In many Infusoria we see one or more pale spots upon 

 the contractile vesicle, which may easily be taken for orifices, 

 but, on closer examination, prove to be only thin spots in the 

 parenchyma of the body and the skin, by which the action of 

 the external water upon the contents of the vascular system is 

 certainly facilitated, so that they probably serve for respiratory 

 purposes. These round clear spots are particularly numerous 

 upon the contractile space of Spirostomum ambiguum. As, 

 therefore, we do not possess the certain proof of one of the most 

 essential requirements of a water-vascular system, the existence 

 of an external orifice, and some things even appear to be directly 

 opposed to it, we can only, like Wiegmannf, Von Siebold, and 

 others, regard it as a blood- vascular system. 



Before passing to the consideration of the nucleus, we will 

 refer to some other conditions of structure, although these have 

 only been detected in particular Infusoria, as the consideration 

 of the nucleus cannot be separated from that of the reproduc- 

 tion, which then still remains to be examined. 



Of other systems of organs, besides the nutritive and circula- 

 tory apparatus already referred to, we have comparatively little 

 to say, and that mostly of a negative nature. If the clear spots 

 already mentioned on the contractile vesicle are not to be re- 

 garded as the indications of a respiratory system, nothing is 

 known of such a system, as Pouchet's supposed respiratory 

 apparatus of the Vorticellce is only their pharynx. The above- 

 mentioned thinner spots in the skin may facilitate respiration, 

 which probably otherwise takes place by the whole skin. 



Nothing is known of organs of secretion, although Ehrenberg 

 describes such organs in Nassula elegans, Chilodon ornatus, and 

 other species, as the sources of a coloured gastric juice ; but the 

 coloured spots which they are said to form are regarded by 

 others (Von Siebold) only as pigment-spots. In most, if not 

 all Infusoria the whole surface of the body is capable of exuding 

 a gelatinous matter. Some do this regularly, and the gelatinous 

 matter exuded either retains its gelatinous consistence {Stentor, 

 Chcetospira mucicola, and others), or, hardening into a horny 

 voisXi^x {ArcellincR, OphrydincSy Tintinnus, Chatospira MullerijSzc), 

 forms a sheath (urceolus) into which the animal can retract itself 

 more or less completely. In some species of the genus Difflugia 

 grains of sand are stuck into this hardening sheath; in the 

 Polythalamia it becomes calcified. Besides this exudation of 



* Froriep's Notizen, 1849, p. 6, and Vergl. Anat. p. 220. 

 t Archiv, 1835, i. p. 12. 



15* 



