and Laboratory Methods. '^099 



CURRENT ZOOLOGICAL LITERATURE. 



CHARLES A. KOFOID, University of California. 



Books and Separates of Papers on Zoological Subjects should be Sent for Review to Charles A. 

 Kofoid, University of California, Berkeley, California. 



Sobotta, J. Ueber die Entwickelung des Eggs of several members of the salmon 



Blutes, desHerzensunddergrossenGefass- family, fertilized at the fish hatchery, 

 stamme der Salmoniden nebst Mitteilungen •' ■' ' 



uber die Ausbildung der Herzform. Anat. were reared in running water in the 



Hefte. Abth. 1,19:579-684, Taf. 23-32, laboratory from the two-cell stage 

 190^2. ■' * 



to the hatching period. Living em- 

 bryos of early stages may be examined if freed from the yolk in normal salt 

 solution. Embryos were preserved as follows : Eggs were first placed for two 

 minutes in a small amount of chrom-acetic mixture (2 per cent, chromic acid 4 

 parts, glacial acetic acid 1 part). As soon as the embryo begins to become 

 opaque the eggs are transferred to 2 per cent, chromic acid, in which they lie 

 until the embryo and germ disk are thoroughly penetrated by the fixing fluid. 

 This occurs in about one and one-half hours and before the yolk is affected by 

 the reagent. The embryo is easily seen through the egg-shell, which is then 

 opened at the opposite pole and the yolk removed beneath the germ disk by 

 a fine pipette. This should be done in normal salt solution, since water curdles 

 the yolk of teleosts. This process leaves the first protoplasmic structures intact 

 and permits the removal of the earliest stages from the egg-shell. The embryos 

 are then placed for one and one-half hours in picro-sulphuric, sublimate, or better 

 still, in picro-sublimate for final fixation. After alcohol grades, with iodine treat- 

 ment in case of sublimate material, the embryos were stained /// toto in borax 

 carmine, Bohmer's haematoxylin, or a combination of the two. In this method, 

 which is applicable to all yolk-laden eggs of other teleosts, the egg is freed from 

 all hindrances to the most perfect embedding and sectioning and also from the 

 distortion and uneven preservation found in eggs fixed by the usual methods. 

 The author insists that the whole of the protoplasmic cap remains intact and free 

 from distortion. Chromic acid is the main fixing agent. The removal of the 

 acetic acid at an early stage prevents the swelling of the yolk and consequent 

 distortion of the embryo by pressure against the egg membranes. The after 

 fixation serves to increase and prolong the stainability of the tissues treated by 

 the chromic acid. 



The author prefers Bohmer's haematoxylin to all other alum hsematoxylins as 

 a result of ten years' experience. The remnants of old stock are always added 

 to new solutions to assist in the process of ripening. Embryos are passed to 

 distilled water until they sink, then to 5 per cent, alum solution until thoroughly 

 saturated. They are then stained in Bohmer's haematoxylin, full strength, or 

 diluted one-half with the alum solution. The over-stain is washed out in the 

 alum solution until the desired tone is secured. Transverse, frontal and sagittal 

 sections were cut, in all about 150 series representing a large number of stages. 

 Infiltration was accomplished by the chloroform-paraffin method. The exposure 



