432 APPENDIX. 



appearing as if at this part the parietes of the latter had been drawn 

 inwards. On two sides of this hollow there are dark transverse lines, 

 rather more distinct on one side than on the other, indicating the com- 

 mencement of the transverse ruga? of the neck, mentioned in the description 

 of this part in the perfect animal, in which the laminated earthy bodies 

 are contained. About the central part of the cervical projection there is 

 an ill-defined oval space, having a granular appearance, and containing 

 some minute spherical particles of a dark colour, consisting apparently of 

 a highly refractive material. In this condition of the entozoon there is 

 nothing in this space which has the slightest resemblance to the parts 

 which are there about to be developed, namely, the booklets, suckers, and 

 earthy concretions ; and it is only by the comparison of these obscure 

 appearances with the other specimens in which the development of the 

 hooklets is a little more advanced, that their true signification can be 

 learned." 



The author here proceeds to describe the development of the 

 hooklets, and continues — 



" From the facts that have just been mentioned, the hooklets of the 

 animalcule in question do not appear to be formed by cell-development. 

 For by the most careful examination of these organs, both recent, and 

 after the application of acids, I have not been able to distinguish anything 

 which can be looked upon as a cell or cell-nucleus, calculated to give the 

 idea of their being developed from previously existing cells, or in depen- 

 dence of cells ; but, on the contrary, all the various forms and characters 

 which they present during the process of their formation simply indicate 

 the coalescence of very minute spherules of an homogeneous material, 

 exceeding the number of a complete set of hooklets, into small globular 

 masses, and these again into larger pieces, and so on successively, until 

 recognisable portions of hooklets come into view, which, coalescing, build 

 up, as it were, an entire organ. 



" It is worthy of remark, that if these structures had been produced 

 directly from the metamorphosis of previously existing cells, the circum- 

 stances connected with their formation would have been the most 

 favorable for observing both the original cells and the changes which 

 they passed through ; indeed, so much so, that is almost impossible that 

 they could have escaped notice. First, because these parts are of such a 

 size and degree of transparency as to admit of examination with the 

 highest powers of the microscope without the necessity of disarranging 

 them, or disturbing their position by manipulation. Secondly, because 

 the material of which they are composed is so dissimilar in appearance to 

 that forming the adjacent tissue, and so characteristic that it cannot be 

 confounded with the structures in their immediate vicinity. Thirdly, 

 because at one view, in a favorable specimen, hooklets can be seen in 

 every stage of their formation, from the first grouping together of the 

 masses of formative particles to the blending of them into perfect organs ; 

 and lastly, because it is not as if a mere thread of tissue were formed 

 amongst other threads, slightly differing in appearance, as fibres of elastic 

 tissue, for instance, in a mass of connective tissue, but the objects referred 

 to are perfect organs, which possess an arrangement of parts connected 

 together with order and remarkable regularity. So that, under such 



