2098 Journal of Applied Microscopy 



inates from muscle cells. In Sarcophagus there are three methods of muscle 

 insertion. In one the end of the muscle loses its striation and its fibrils pene- 

 trate the matrix cells of the chitin to become attached directly to the chitin itself- 

 The part becoming attached to the chitin can no longer be stained by iron hae- 

 matoxylin, but readily takes up congo-red. The second way shows the muscle- 

 cells losing their striation on reaching the epithelium, they then divide into a 

 number of branches which pass between the epithelial cells to the chitin layer. 

 These lose their primitive fibrillae in the chitin, where they are chitinized as in 

 the preceding instance. In the other cases a union takes place between the mus- 

 cular and epithelial fibrillae, and these after penetrating the epithelial cells become 

 fastened to the layer of chitin. The author concludes that there is no continuity 

 between the sarcoglia of muscle-cells and the substance of the epithelial-cell, 

 since the membrane is complete. Also that there are two kinds of fibrillae present 

 in epithelial cells, normal ones and those which take part in muscle insertion ; 

 these are distinguished by their different appearance and staining reactions. 

 Moreover, the muscular fibres pass over into fibrillae without undergoing any 

 change in appearance or staining powers ; these fibrillae are directly continued 

 into the epithelial cells. In Sarcophagus carnaria there are three kinds of cell 

 bridges, those uniting epithelial cells to each other, those uniting muscle cells to 

 each other, and those uniting epithelial and muscle-cells. In the last case the 

 bridge is formed by a sarcoglial process from the muscle-cell uniting with a pro- 

 cess from the epithelial cell. 



On the morphological significance of chitin in insects the author says that all 

 vertically striated chitins, whether single or many layered (in insects), are mor- 

 phologically and phylogenetically only stiffly chitinized and united cilia. This 

 statement rests on the fact that there is in all chitin matrix-cells examined, at the 

 outer end a series of blepharoblasts with which the columns of chitin-forming 

 substance are directly continuous; these blepharoblasts being homologous to 

 the thickenings found at the bases of cilia. The author shows a most interest- 

 ing series of facts to support these statements. a. m. c. 



V. Schumacher, Dr. S. The Yolk Organ of The author shows that in spite of a 

 Salmo fario. S. B. K. Akad. Wifes. Wien. , . , i ^l 



109: 675-00 iQoo. • large amount of research on the em- 



bryology of bony fishes little is known 

 of the absorption of the yolk sac. He studied it in the river trout. It is well 

 known that in this fish the communication between the enteron and the yolk sac 

 early disappears. When the fish hatches, its yolk-sac hqs in the center an almost 

 homogeneous mass of yolk; around this is a layer containing yolk spheres and 

 prolongations of the protoplasmic sheath, the latter surrounds the median layer 

 on its outer side. The yolk consists of these three layers. Outside the yolk is 

 an endothelial layer, the splanchnopleure, separated from the somatopleure and 

 body wall by a slight ccelomic cavity. At the time of hatching the protoplasmic 

 layer of yolk contains oval yolk-nuclei, constituting a yolk syncytium; at a later 

 stage these disappear and in their place are bodies of irregular shape staining as 

 nuclei. They are the remnant of degenerating vitelline vessels that finally dis- 

 appear entirely. The author ascribes considerable importance to the protoplas- 

 mic layer as an agent in yolk absorption, both in earlier and later stages, but 

 also considers that the peritoneal epithelium of the sac is an active agent in the 

 process. a. m. c. 



