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III.- — Beproduetion and MuUipUeation of Diatoms. 

 By the Abbe Count F. Castraoane, Hon. F.E.M.S. 



(Bead 9th January, 1889.) 



It is now about thirty years since I first entered upon the study of 

 Diatoms ; and from that time down to the most recent discoveries I 

 have followed the progress of photography, desirous of making a 

 serious use of this marvellous art ; from the conviction of the value of 

 its employment for the purpose of faithfully reproducing diatoms 

 enlarged under the Microscope. This I at first did only for my 

 enjoyment, contenting myself with communicating to my friends the 

 results obtained. The encouragement received from my friends and 

 from experts, and the desire expressed by such as De Notaris, Cesati, 

 Brebisson, and Meneghini, overcame my reluctance to make known 

 the modest results of my studies; so that since 1867 I have 

 imposed upon myseK the duty of publishing my observations. From 

 that time not a year has passed without my contributing notes which 

 may be found in the English quarterly and monthly microscopical 

 journals, the Proceedings of the Italian Society of Cryptogamists, and 

 in various other Italian and foreign pubhcations ; but chiefly in the 

 Proceedings of the Accademia Pontificia dei nuovi Lincei, in which 

 I have taken part as an ordinary fellow since 1867. 



During these first years I was fortunate in making some remarkable 

 observations on the act of reproduction of a Podosphsetiia, which induced 

 me to devote special study to the biological laws of the diatoms. As 

 the result of this, on being invited to take part, in 1874, in the Inter- 

 national Botanical Congress at Florence, I presented on that occasion 

 a memoir on the process of reproduction in diatoms, which was pub- 

 lished in the Proceedings of that Congress. In the publication of 

 this memoir I ought, in the opinion of Dr. Pfitzer, to have made the 

 remark that, while my conclusions were founded on positive observa- 

 tions in certain cases, I was not in a position to generalize from them. 

 After this, enlarging my connections with the most famous micro- 

 scopists, I had often the satisfaction of seeing myself spoken of 

 in the journals as a specialist in diatomology; and finally, I was 

 most unexpectedly invited to report on the diatoms collected in the 

 * Challenger ' expedition. 



Nevertheless, I frequently met with works on diatoms more or 

 less complete, in which I found a restatement of views on the mode of 

 reproduction and multiplication, incorrect on points of some import- 

 ance, which I had persuaded myself that I had confuted. Far from 

 wishing to impose my ideas merely because I am myself profoundly 

 convinced of their truth, that which I have always desired, and have 

 expressly proclaimed (though hitherto ineffectually), is that my opinions 

 should be discussed in the interests of Science and of Truth, which ought 

 to be the sole, or at least the first, aim of our studies. There is nothing 



