io6 



THE AMERICAN MONTHLY 



[June, 



a few pages before. We read as 

 follows: (page 211), " mes obser- 

 vations sur la conjugaison des Vor- 

 ticelliens (compt. rend. acd. d. sc. 

 1875), o"t e'te' effectue'es sous I'empire 

 des idees que je m'e'tais faites de ce 

 phenomene oil je voyais un processus 

 de reproduction sexuelle, car le grand 

 memoir e de Biltschli, qui m\i ounert les 

 yeiix sur sa signification re'elle, n^a paru 

 que Panjie'e suivante." 



I would ask how Balbiani could 

 properly designate me as an investi- 

 gator, if I succeeded so far as to 

 leave the domain which he worked 

 up less enlightened. In the above 

 cited passage there remains nothing 

 but the assertion, that I refused to 

 recognize the "generation sexuelle" 

 of the Infusoria, which Balbiani had 

 discovered twenty years ago, and 

 Balbiani is now more than ever con- 

 vinced, that the Infusoria while in 

 conjugation form a "generation sex- 

 uelle." The way he tries to explain 

 it now is, that the Infusoria are 

 hermaphroditic cells, with a female 

 germ (the secondary nucleus), and one 

 or more male or primary germs or 

 nucleoli. 



This view was propounded first by 

 O. Hertwig*, as Balbiani incidentally 

 mentions, and therefore no credit is 

 due the latter: During the conjuga- 

 tion the capsules of the nucleoli are 

 sfiid to be partly exchanged between 

 the two individuals, and therein con- 

 sists the proper fertilization, /. e., the 

 entrance of a male germ into another 

 infusoria individual. 



Instructions in Dry-Plate 

 Photography. 



( Contiimedfrom paj^e S8.) 



After the negative is fixed and dried 

 it should be examined to see that 

 there are no defects, and if quite satis- 

 factory it may then be varnished. It 

 is advisable to purchase a varnish for 



*Beitragezur Kenntniss der Bildung und 

 Theilung des thierischen ties. Morphol. 

 Jahrbuch, i. Band, p. 347. 



the purpose, rather than to undertake 

 the trouble of making one. The 

 varnish should be thin. It is applied 

 by pouring a quantity upon the plate 

 held in the hand, causing it to flow 

 over every part and then pouring it 

 off into the bottle again. The thin 

 film dries in a few moments, when the 

 negative is ready for use, unless some 

 pin-holes and bad spots are observed 

 which require to be removed by the 

 artistic use of a pencil, in which case 

 the novice had better take some in- 

 structions, in retouching negatives 

 from a practical photographer before 

 attempting to remove them. 



When, owing either to insufficient 

 exposure or to improper development, 

 the negative is too thin to yield good 

 prints it should be intensified before 

 it is varnished. We give two methods 

 of intensification, the first of which is, 

 we believe, most frequently employed, 

 but the second we have used with 

 great satisfaction, and in some cases 

 it seems to yield the most excellent 

 results of any process we have tried. 



If possible, avoid the necessity of 

 intensifving. Make the exposures 

 with judgment, and develop so as to 

 obtain sufticient density without any 

 after treatment. In spite of all care, 

 however, it will sometimes be neces- 

 sary to resort to intensification. But 

 the beginner must learn that a negative 

 that looks very thin will sometimes 

 print well. A few experiments will 

 show how dense the negative must be 

 to yield good prints. The two methods 

 of intensifying will now be described. 



I. Mercury intensifier. — Three solu- 

 tions are first prepared as follows : — 



a. Mercuric chloride 

 (corrosive sublimate), 60 grains. 

 Water, 4 ounces. 



/;. Potassic iodide, 90 grains. 

 Water, 2 ounces. 



c. Sodic hyposulphite 120 grains. 

 Water, 2 ounces. 



Add b to a, which will throw down a 

 precipitate of mercuric iodide, and 

 then add c which will redissolve the 

 precipitate more or less completely. 

 The solution will then be ready for 



