THE 



MONTHLY MICROSCOPICAL JOURNAL. 



MAY 1, 1872. 



I. — Mesearclies on the First Singes of the Development of the 

 Common Trout (Sahno fario). By Dr. E. Klein. 



(Head before the Royal Microscopical Society, March ij, 1872.) 



Plates XVI. and XYII.' 



EuscoNi* was the first to describe the segmentation of the blasto- 

 derm of tlie egg of Teleostean fishes. His observations were made 

 on the Cyprinoids, and he states that the mode of segmentation is 

 quite of the same type as that of the Iktrachia, known by Prevost 

 and Dumas in 1824, and by Eusconi himself in 1826. The state- 

 ment of Eusconi was confirmed by Lereboulletf for Pike and Perch ; 



EXPLANATION OF PLATES XVI. AND XVII. 



Development of the Trout. 



Figs. 1, 2, 3, 4, 5, and 6. — Showing the different stages of segmentation of tho 

 blastoderm, a, blastoderm. '<, yolk. 

 ,, 7 A and 7 B. — Showing the bla.stoderm of different stages in tlie profile. 



a, vitelline membrane, b, blastoderm, c, fat-globules of the yolk. 

 Fig. 8 a, 1 and 2. — Elements of the blastoderm of four days. 



„ 8 A, 3, 4, and 5. — Elements of the blastoderm of seven days. 



„ 8 a and b. — Elements of the blastoderm of ten days. 



,, 9. — Vertical section through the blastoderm of three days, a, blastoderm. 



6, yolk of the saucer-like depression. 

 „ 10. — Vertical section tlirough the blastoderm of six days, a, blastoderm. 



b, yolk, c, fat-globules of the same. 



,, 11. — Vertical section through the blastoderm of twelve days, a, blastodeim. 

 6, segmentation cavity, c, large elements on the bottom of the cavity. 



d, superficial layer of flattened cells of the blastoderm, e, yolk. 



„ 12. — Vertical section through a blastoderm of fourteen days, a, segmenta- 

 tion cavity. ^, peripheral swelling of the blastoderm, c, superficial 

 layer of flattened cells of the blastoderm, d, lower layer of cells cf 

 the thinner part of the blastoderm, e, large elements on the bottom of 

 the cavity. /, yolk, g, fat-globules of the yolk. 



,, 13. — Vertical section through the embryo of eighteen days, a, superficial or 

 corneous layer, b, second or nervous layer, c, third or motoric-germi- 

 native layer (middle layer), d, lower or epithelio-glandular layer. 



e, yolk. /, central nervous system, g, chorda doraalis. 



* IMiiller's ' Archiv,' 183t5. f ' Annales des Sciences,' 4 S , T. 1, 2. 



VOL. Til. V 



