274 Mr Meyen on the Digestive Organs of the Infusoria. 



thing in common witli the balls of which we have spoken, al- 

 though the latter may get into them singly ; but this can only 

 be considered as accidental. We may trace the fonnation 

 of these cavities, and perceive their sudden and complete dis- 

 appearance, with as much ease as the formation of the balls. 

 Nay more, it is sometimes possible to see how one of these 

 cavities moulds itself over a ball, and speedily afterwards dis- 

 appears. The microscope shews that these cavities are not 

 lined with a particular membrane, but are mere excavations 

 of the pulpy substance. They likewise often appear very near 

 the inner surface of the membi'ane which forms the skin of the 

 animal, and some of them increase to such a size that their 

 diameter is equal to the third or the half of that of the entire 

 cavity of the infusoria. The slight refraction which the rays 

 of light imdergo at their circumference, proves that these ca- 

 vities are not filled with air, but by a liquid ; and in the large 

 infusoria, it is easy to satisfy ourselves that they do not open 

 on the exterior. Similar cavities are formed in the mucus of 

 true cellular plants, particularl}'^ in certain aquatic Cryptoga- 

 mia. 



My botanical labours prevent me from carrying these re- 

 searches farther ; but enough has been said to induce the 

 naturalist to pm'sue them. They require a great degree of 

 perseverance, for it is not easy to establish these facts in all 

 infusoria ; but they are of high importance, since the order 

 Polygastria has already been admitted into many modern 

 treatises on Zoology. 



Researches on the Structure of the Scales of Fishes. Bjr Dr 

 L. Mandl. With an illustrative Plate. Continued from 

 page 126 of this volume. 



We have learned from the first chapter, which gives a his- 

 torical sketch of the researches which have been made on 

 tegumentary appendages, that all authors agree in considering 

 these tissues as produced by a secretion, and formed by homo- 

 geneous layers, similar to those observed in the shells of hi- 



