I 



OF THE PROTOZOA. CILIATA. 337 



changes they may visibly undergo from the action of external agents, from 

 age, and other conditions, is at present too imperfect to signalize certain par- 

 ticles, definable by no sufficient characteristics, as special structures, such as 

 ova, — unless, indeed, we can watch their origin, growth, extrusion, and de- 

 velopment into animalcules assuming the particular form and organization of 

 the parent animal at an earlier or later date. Perty, indeed, has imagined — not 

 proved — certain minute organisms floating in the \icinity of an animalcule, 

 ha\'ing about the same size as the supposed internal ovules, to be the young 

 resulting from those gemis ; and although it cannot be denied that he is in 

 the nght, yet it is for him to show that he is so, by elucidating the phases of 

 development ; and we must always keep in view the very erroneous fancies 

 which result from these supposed relations between contiguous organisms, 

 very probably only accidentally brought together, — of which we have an 

 illustration in the visionary hypotheses of spontaneous development and 

 ascendant embryogeny put forth by Gros and others. 



^Ye have stated the preceding objections against the particular statements 

 of Carter and Perty, and not against the hypothesis of the production of in- 

 ternal germs ; for sufficient examples are on record of the production of such 

 germs and of living embryos within animalcules, after preparatory develop- 

 mental changes, from the fission and breaking up of the nucleus. Before leaving 

 this hypothesis of the existence and development of internal germs, it is but 

 right to mention that it has been received, among others, by Eckhard and by 

 Oscar Schmidt, both of them supporters, in almost all their details, of Ehren- 

 berg's \iews, and who are believed by most authorities to have too much the 

 character of advocates of a particular theorj^, to discuss or to observe in ge- 

 neral without prejudice. To allude briefly to their observations, Eckhard 

 (A. N. H. 1847, xviii. Suppl. p. 446) in the first place remarks, as others 

 have done, on the very difiPerent sizes of animalcules of the same species, as 

 a proof of ovular development, arguing that the very smallest cannot result 

 from fission or gemmation. To this he appends an observation made on 

 Stentor cceruleus (XXIX. 8), which, from its completeness and apparent 

 truthfulness, deserves quotation when we come to speak of the development 

 of ova. Schmidt corroborates Eckhard's statement of the production of 

 living germs from Stentor cceruleus, and affirms, in addition, that germs are 

 frequently extruded and developed outside the parent, and that their subse- 

 quent development from minute globular and conical transparent and almost 

 colourless organisms, with long cilia, may be watched thi^ough all the inter- 

 mediate stages until the complete animalcule, with its spiral ciliary wreath 

 and mouth, is perfected. 



The preceding speculations on the development of ovules and germs have 

 their importance materially modified by M. Balbiani's recent researches and 

 hjT^otheses respecting the prevalence of a sexual mode of reproduction among 

 the Ciliata, as detailed above (pp. 329-334). 



Spermatozoids ( ? ). — This term is provisionally applied by Mr. Carter to 

 granules originally developed from the nucleus in Amoeha^ Euglypha, and 

 Spongilla, and supposed by him to impregnate the o^^lles. " With reference 

 to the organs of generation," he wiites (A. N. H. 1856, xviii. p. 228), " in 

 the other Infusoria, I can state no more than that, although there is a fusiform 

 nucleus in Otostoma (XXVIII. 25, 2Q), I have also constantly seen a bunch 

 of string-like filaments floating about its inteiior, which appeared to be at- 

 tached near the buccal ca\ity ; and although I could make out nothing more, I 

 could at the same time only liken these to the generative apparatus in the 

 Planaria mentioned, which floats round the buccal cavity and upper part of 

 the membranous stomach in a similar manner." 



