AND ON THE DIRECT AGENCY OF THE SPERMATOZOON. 267 



egg of the Frog, as they show, conceived that this body becomes, not the embryo itself, 

 but the foundation of the nervous system of the embryo. Since then, Dr. MARTIN 

 BARRY announced to the Royal Society that he had seen spermatozoa within the 

 substance of the egg of the Rabbit ; through the envelopes of which, he has stated, that 

 there is a natural perforation or cleft at the time of fecundation* ; a view which has 

 met with much opposition, as no physiologist has hitherto (1852) verified his observa- 

 tion with regard to the existence of a perforation or cleft in the egg-envelopes ; or 

 has announced that he has seen the spermatozoon within the ovurn of that animal. 

 Indeed so general has been the opinion that there is no penetration by the sperma- 

 tozoon, even into the envelopes of the egg, notwithstanding WAGNER'S-^- announce- 

 ment that he had seen spermatozoa within the envelopes in the eggs of Fishes, that 

 one of the most recent investigators, M. QUATREFAGES, in alluding to MM. PREVOST 

 and DUMAS' views, observes, that " it is useless to allude to the question of penetra- 

 tion by the spermatozoon, as he believes that the only living author of the theory has 

 himself renounced it|." But very recently it has been announced, in a paper on 

 the Ascaris Mystax, by Dr. NELSON, communicated to the Royal Society , that the 

 spermatozoon in that animal does penetrate into the substance of the yelk ; and a 

 somewhat similar account of that of the Earth-worm was formerly given by Dr. ARTHUR 

 FARRE||. Yet, with all due respect for the observations of these able investigators, I 

 must still have hesitated to admit the fact of any penetration, even into the envelopes 

 of the egg, had I not more recently been convinced of this fact by direct observa- 

 tion, in correction of my former opinions, in so far as relates to the penetration of 

 the spermatozoon into the envelopes of the eggs of the Frog, and its arrival at the 

 vitelline membrane. To them, then, be all honour on this subject, while I subjoin 

 my testimony to a fact which I had heretofore failed to observe. 



It was during the month of March last (1852), while making experiments on the 

 Frog's egg by artificial impregnation, before some scientific friends, that certain 

 appearances were noticed beneath the microscope within the expanded jelly of the 

 egg, which led to a suspicion of the probability of penetration by the spermatozoon. 

 Heretofore I had employed, in my observations, either a deep glass cell, in which the 

 egg was completely immersed in water, or the common object-glass of the microscope. 

 In the experiments now referred to, a shallow glass cell was employed, which was 

 capable of containing only a single egg. This, while it admitted light freely around 

 the egg, was too shallow for its complete immersion, and the egg was therefore 

 covered by a drop of water, into which the object-glass of the microscope was passed, 



* Philosophical Transactions, Part II. 1840, p. 533, Plate XXII. figs. 164, 165 and 167. Ibid. Part I. 

 1843, p. 33. 



f Elements of Physiology (English Edit, by Dr. WILLIS), note, p. 74, 1841. 



I Annales des Sciences Nat. 3 me Se"rie, torn. xiii. 1850. 



Proceedings, June 19, 1851, vol. vi. p. 86. Philosophical Transactions, 1852. 



|| See Dr. CARPENTER'S Principles of Human Physiology, 1st edit. 1842, p. 617. 

 MDCCCLIII. 2 N 



