JOURNAL OF MICROSCOPICAL SCIENCE. 



EXPLANATION OF PLATES IX, X, XI, 



Illustrating Nikolas Kleinenberg's paper on the Develop- 

 ment of the Earth-worm, Lumbricus trapezoides, 

 Duges. 



The references are the same in all the figures. 



as. Aperture of the segmentation cavity. cb. Buccal cavity. cc. 

 General body cavity or cavity of the zoonites. cd. Digestive cavity. 

 cm. The large primitive cells of the mesoderm (mesoblasts). com. 

 Commissure of the oesophageal collar. cs. Segmentation cavity. 

 ?f<- • -ew-: Cord uniting the twin embryos, or its single cells. ec. Ectoderm. 

 en. Endoderm. eo. Ectodermic epithelium of the mouth and of the 

 oesophagus, gc. Cephalic ganglion. Iso. Somatic lamina. Isp. 

 Splanchnic lamina. m. Muscle plate. mes. Mesoderm. n. 

 Ventral nerve-cord. pc. Cephalic germinal streak. pp. Primi- 

 tiv e ventral germinal streak. sn. Ventral furrow. 



PLATE IX. 



Fig. 1. — Segmented egg, seen from above. 



Pig. 2. — Germinal bladder formed of a single layer of cells. The segmen- 

 tation cavity opens externally. Pigs. ] and 2, Zeiss' objective DD, 

 ocular 3. 



Fig. 3. — Solid germinal sphere, in which the rudiments of the layers for the 

 first embryo are visible. 



Fig. 4. — A. rather later stage, in which the formation of the second embryo 

 Las begun. Longitudinal section. 



Pig. 5. — Longitudinal section of a more developed stage. 



Pig. 6. — Twin-embryos. The one on the right hand is rather the more 

 developed. 



Pig. 7. — Embryos nearer the period of separation. 

 Pig. 8. — Longitudinal section of a double embryo, in profile. 

 Pig. 9. — Longitudinal horizontal section of the same. 

 Fig. 10. — Advanced embryo developing the second embryo in the form of 

 a bud (X). 



N.B. Pigs. 2 to 10 represent optical sections. 



Fig 11«. — Transverse section of the posterior end of a very young 

 embryo. 



Pig. 11^. — Prom the same embryo more in front. 



Fig. 12. — Transverse section of the posterior part of a more developed 



embryo. 

 Pig. 13. — Section through the middle of the body of a more advanced 



embryo, f. Fissure in the mesoderm. 

 Pigs. 3 to 13. Zeiss' obj. P, ocul. 1. 



Pig, 14. — ^The lower part of a section of the anterior extren)ity of a more 

 developed embryo. Obj. DD, ocul. 3. 



