460 



GENERATION. 



of the more common animals in parts of a 



line:* 



Parts of aline, 

 Helix pomatia .................. '410 



Lymneus stagnalis .............. -300 



Aquatic Salamander ............ -200 



Viper ......................... -050 



Polecat 



Guinea-i 



Mouse . . ................... V '040 



Linnet 



Sparrow 



Hedgehog ................... \ 



Anguis fragilis ................ S 



Bull ........................... -028 



, *. 



-Fg f 



Mii r 



030 



Goat 



Rabbit 



Common fowl '016 



Frog -013 



L)og ) 



Man (according to Der Gleicheri) J 



Man (according to Buffon) "006 



Gruithuisen states that he has observed the 

 seminal animalcules to propagate by division 

 of their bodies, or fissiparous generation. But 

 we are far from attaching implicit faith to all 

 that has been stated even as matter of observa- 

 tion regarding these bodies. 



W ? e ought not to omit in this place to state 

 another and a different view which has recently 

 been taken of the nature of the moving particles 

 of the semen ; we mean that of G. Treviranus, 

 who, founding chiefly upon observations made 

 by himself in the lower animals, as Mollusca 

 and Insects, adopted the opinion that these 

 particles are not independent animals, but ana- 

 logous in their structure and properties to the 

 fibrils and particles occurring in the pollen of 

 plants. Their motion he seems to regard as of 

 the same kind with that discovered by R. Brown 

 to exist in infusions of these and other minute 

 floating particles, and not as of an animal or 

 spontaneous kind. He deduces this conclu- 

 sion principally from the alleged observation 

 that the motion of the so-called animalcules is 

 not the same as that of ordinary Infusoria, but 

 differs from it in this respect, that it is simply 

 vibratory and constant, and not interrupted by 

 any of those stops or pauses and changes from 

 place to place which are held to indicate spon- 

 taneity in the motions of Infusoria.f 



Some of the facts already stated by us shew 

 the fallacy of the opinion of Treviranus. Baer, 

 who regards the Spermatozoa as distinct living 

 animals, holds that Treviranus has observed 

 only an imperfect condition of the animalcule, 

 and states in the work of BurdaehJ some addi- 

 tional observations of his own made in the 



* This table is taken principally from the mea- 



snail, which promise, when pursued further, to 

 remove some of the difficulties respecting the 

 nature of these bodies. Baer states that he has 

 observed the head and tail parts to become 

 separated from one another, and both these 

 parts, but especially the tail, to move about 

 after separation. Baer has observed also that 

 there are various stages of formation and change 

 of the seminal animalcule, during which not 

 only their form but also their motions undergo 

 remarkable alterations, and he supposes that 

 Treviranus must have observed the spermatic 

 animalcule of the snail and mussel in one of 

 these stages only. Observations made* by 

 the author of this article and by Dr. Sharpey in 

 the frog, seem to bear upon this point, and to 

 be in some degree confirmatory of the view 

 given by Baer. We have almost invariably 

 found, in observing the seminal fluid of the 

 frog in the spring or summer, that the animal- 

 cules contained in it are not of the kind de- 

 scribed by authors in this animal, viz. with 

 both head and tail, but of the thread-like form 

 only. These were collected in bundles in the 

 thick part of the fluid, and generally moved 

 with a continued vibration such as we have 

 previously described. In the thin part of the 

 flnid there were a few round-shaped or monad- 

 like infusoria. Occasionally it happened that 

 when water was added to the thick part of 

 the fluid, and the bundles of the thread-like 

 bodies were artificially broken down, some of 

 them moved progressively through the fluid by 

 the undulatory riggling of one of the extremi- 

 ties ; and during their motion we were surprised 

 to see some of those, which, when at rest, ap- 

 peared to be destitute of any cephalic part, fre- 

 quently assume the appearance of a head. This 

 phenomenon we remarked to be owing to the 

 circumstance that the end by which the animal- 

 cule moved forward was bent backwards on the 

 middle of the body, so as at one time to give 

 exactly the tadpole-like appearance which is 

 represented as a head in their plates by Messrs. 

 Prevost and Dumas. There could be no doubt 

 that this was the case, for in some, in which at 

 one time the end was so closely joined to the 

 body that it could not be seen, at another it 

 loosened from it, and the thread-like animal- 

 cule still continued to progress in the fluid 

 with its curve forwards, and the two ends (of 

 unequal length) floating separate and loose. 

 The author has observed nearly the same phe- 

 nomena in the spermatic fluid of the pigeon. 

 Lastly, the observations of R. Wagner on the 

 spermatic fluid of the Guinea-pig seem to prove 

 more decidedly than any of the previously men- 

 tioned facts that the spermatic infusoria are 

 subject to remarkable changes of form at dif- 

 ferent periods, and that they even go through a 

 regular gradation of development. 



The discrepancy of these observations makes 



These observations were made five years before 



surements of Prevost aud Dumas given in their the publication of this article. For further infor- 



excellent account of the seminal animalcules pub- mation respecting the Spermatozoa we refer the 



lished in the Annalcs des Sciences Naturelles. reader to the articles ENTOZOA and SEMEN ; in the 



t See a paper in Tiedeinann's Zeitschrift, vol. v. last of which Mr. Wagner, who has investigated 



part 2, 1835. 



t Vol. i. second edition. 



their nature with great success, will fully explain 

 his views. 



