32 Proceedings of the Royal Physical Society. 



4. On Salpistes (Stentor) Mulleri and castaneus. (Fig. 11.) 



In the last edition of Pritchard's "Infusorial Animalcules" 

 it is stated that Stentor Mulleri, " when kept long in glass 

 vessels, fasten themselves to the sides, form a slimy covering 

 around them, and die ;" and, further, that Ehrenberg had re- 

 marked that " they would gradually congregate, select some 

 particular spot, and then attach themselves, evincing, as it 

 were, not only a degree of sociality, but a mental activity." 

 In their apprehension of these facts I believe the authors 

 above quoted to be mistaken. It is well known that many 

 aquatic animals have the power of secreting masses of viscid 

 gelatinous matter, which does not readily undergo decomposi- 

 tion, to serve as a nidus for the protection of their ova. Thus 

 the nudibranchiate and other molluscs deposit on stones and 

 weeds long convoluted ribbons of clear firm jelly filled with 

 their eggs, which remain therein until hatched. Many in- 

 sects, aquatic in their earlier stages of existence, adopt the 

 same mode of protecting their young. In the genera Sertu- 

 laria, Plumularia, Campanularia, and Laomedea, species 

 also are found in which the young undergo partial develop- 

 ment whilst still contained in gelatinous cases attached to the 

 exterior of the reproductive cells, as I have already described 

 to the Society in the case of Laomedea lacerata. Other 

 animals employ the same matter to form envelopes or loricse, 

 into which they can retire protected from harm. In this way 

 is formed the "house" of Appendicularia flabellum, of which 

 Mertens has given so marvellous an account, mistaking it for 

 a respiratory organ. Amongst the Hotiferse we find Stephano- 

 ceros, Floscularia, Limnias, Melicerta, and others, each liv- 

 ing privately in its solitary abode, formed either of clear gela- 

 tine, or of the same substance strengthened with mud or other 

 extraneous matters ; while in the genus Conchilos a colony 

 of animals unite their efforts to form a transparent globe, 

 which is rapidly rolled through the water by a multitude of 

 living wheels. Descending to the Protozoa, we may see 

 Ophrydium versatile, an animal scarcely visible to the unas- 

 sisted eye, attaching itself to our tanks by its little speck of 



