44 SPERMATOZOA. 



species of various classes of animals. It was his opinion that they 

 formed the embryo, and that the female's share in the work of pro- 

 pagation was simply the reception and nutrition of the male pro- 

 duct. This view of LEEUWENHOECK'S as to the office of sperma- 

 tozoa in propagation was afterwards entirely rejected : until, in our 

 own century, DUMAS maintained that they form in animals the 

 foundation of the nervous system (the brain and spinal cord) : to 

 which view he was led by a certain resemblance of the first rudi- 

 ment of the embryo (the so-called primitive streak) to a spermato- 

 zoon (Diet. Glassique d'Histoire naturelle, T. vn. 1825. p. 221, 

 article Generation, Annales des Sc. nat. xn. 1827. p. 443-454). 

 But it is not founded on observation, and is moreover sufficiently 

 refuted by the fact that some animals have spermatozoa closely 

 resembling those of mammals, whilst their nervous system has a 

 totally different form from theirs. 



According to WAGNER'S investigations, these active molecules are 

 formed in cells, singly or in bundles : from which, on bursting of 

 the cell-wall, they are set free. In insects they are found as fine 

 threads without a head, or thicker portion: but in most other 

 creatures they consist of a thicker part, the head, and a very fine 

 thread, or tail. The head is, in different animals, of a different 



[The spermatozoon of the Batrachia has an extremely fine mem- 

 brane attached to its tail in the direction of its axis and throughout 

 its whole length by one of the sides, the other being free and wavy. 

 Thus a delicate undulating border is formed. It was discovered by 

 AMICI and rightly described by him, and afterwards by POULET. By 

 others it was mistaken for a thread surrounding the tail with a loose 

 spiral coil. Vid. J. N. CZERMAK, Zeitsch. f. wissensch. zool. B. n. 

 350-355, also VON SIEBOLD, ibid. pp. 356-364.] 



The different memoirs and treatises upon this subject with whose history, as 

 EHBENBERG says, whole volumes might be filled, are not noticed by us 

 that we may not incur a diffuseness unsuitable to the limits of this manual. 

 R. WAGNER'S Lehrbuch der speziellen Zoologie, 2 te Auflage, Leipsig, 1843, 

 8vo, s. 10 30 may be consulted with advantage. It gives a full account of 

 the most important discoveries of the author and of other contemporary 

 observers. [This work has been translated into English by Dr Willis. 

 Comp. the later work of R. WAGNER and R. LEUCKART, Aricle Semen in 

 TODD'S Cyclop, of Anat. and PJiysiol. Vol. rv. p. 849.] 



