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extreme ends are best adapted. When one of these ends is about 

 to have an addition made to its length, the investing membrane 

 at this part becomes at first very thin, and then disappears. A 

 clear space is next seen, having in some specimens the form of the 

 part which is about to be added to the extremity of the entozoon ; 

 in others it has no defined limit. This space contains, in some 

 cases, nothing but extremely minute molecules, of different 

 shapes; in others, these molecules are mixed with granules of 

 various sizes, which have every appearance of having been pro- 

 duced by the coalescence of the molecules ; and lastly, with these 

 molecules and granules, there are in other examples very distinct 

 globular cells, of a bright aspect, looking more like nuclei than 

 perfect cells ; these soon become flattened oval, and ultimately take 

 the elliptical form before described. All the time these changes are 

 taking place in the molecules and cells, the membrane has been in 

 progress of formation, so that when the molecules have disappeared, 

 and their place has become occupied by perfect cells, the end of the 

 animal is completed. The cilia are soon afterwards added. The 

 lateral growth of these animals takes place in the same manner: the 

 first indication is a separation of the cilia, which, it must be observed, 

 are larger at the sides of an entozoon than at the extreme ends ; 

 and then a thinning of the membrane supporting them ; and, lastly, 

 the formation of globular cells, as before noticed. After the animals 

 have become of a considerable size, and forced their way from the 

 interior of the primary fasciculi into the cellular spaces between 

 the larger muscular fibres, they still continue to grow, especially 

 in breadth ; but they lose their cilia, and gradually acquire those 

 parts which have been described as belonging to the neck. The 

 first evidence of this addition is the appearance of inversion of the 

 middle part of the cyst, forming a small hollow, the sides of which 

 look as if thrown into folds containing granular matter, and the 

 bottom presents a circular space in which are granular particles of 

 various forms and sizes, but those in the centre are darker than the 

 rest. It is from these particles that the suctorial disks, the hook- 

 lets, and the first of the laminated bodies are about to be formed, 

 but as yet none of these parts are recognizable. At a stage a little 

 more advanced, this apparent inversion of the cyst has increased, 

 the neck has become longer, and the appearance of disks, hook- 



