6o ORGANIZATION OF THE INFUSORIA. 



attached or sedentary species. Among the former are necessarily included 

 those variable and often exceedingly beautiful vase-like or tubular structures 

 upon which the titles of sheaths or loricae are most usually conferred, and 

 likewise those investments of simple mucus subservient in a similar manner 

 as a dwelling house for the habitation and protection of the one or many 

 animalcules who are engaged in its construction. Within the category of 

 " excreted structures " have also most essentially to be included those 

 hermetically closed indurated cysts or envelopes exuded by almost every 

 known type of animalcule' under certain uncongenial conditions, and also 

 very frequently as an accompaniment of the phenomena of binary division 

 or sporular reproduction. The excreted structures pertaining to these 

 last-named special purposes possessing an altogether independent signifi- 

 cance, they are treated of separately later on under the respective titles 

 of " encystment " and "sporular multiplication." 



In all of the foregoing cases it is evident that the secreted structure is the 

 direct product of exudation or simple separation from the external layer or 

 ectoplasm of the contained animalcule, and is indeed in many instances 

 scarcely to be distinguished from the outermost or true cuticular element of 

 the several layers of the ectoplasm already described at length. Instances 

 in which the closest affinity may be said to subsist between these two 

 structures are afforded by, and specially referred to, in the account given 

 of the members of the genus Lagcnophrys and of Opercularia nutans. In 

 its simplest form, and yet at the same time partaking of the character 

 of an independent exuded structure, the secreted envelope has a purely 

 gelatinous consistence, and corresponds essentially in nature and aspect 

 with the exuded mucilage that constitutes the common envelope of various 

 bacterial growths in the characteristic " gloea " phase of their existence, and 

 is similarly associated with many other low-organized plants or Phytozoa. 

 Instances among the higher or Ciliate group of the Infusoria, in which a 

 simple mucilaginous investment takes the place of an indurated sheath or 

 lorica, are of comparatively rare occurrence, the genera Ophrydium, Ophio- 

 nella, Chcetospira, and certain species of Stcntor, yielding the most prominent 

 exceptions. Among the Flagellata such mucilaginous investments, and more 

 especially when pertaining to colonial or sociably aggregated types, are far 

 more frequent, such genera as Uroglena, Protospongia, Spongomonas, and 

 PJialansteriuin being especially noteworthy in this direction. The transition 

 from a simple gelatinous sheath to a comparatively hardened test or lorica 

 is very gradual, and is well exemplified among the members of the genus 

 SalpingcBca, in several of which, as, for example, 5. ampulla, the development 

 of the highly characteristic lorica from a primary simple mucilaginous exu- 

 dation has been attentively observed. The composition of the loricae 

 throughout the various orders and families of the infusorial class is found to 

 exhibit a very uniform character, being represented in most cases in its 

 matured state by a more or less brittle material, having an apparently chiti- 

 nous consistence. In the majority of instances these loricse are perfectly 



