and Laboratory Methods. 2097 



peculiar in Alchemilla, some or all of these five nuclei retaining the power of 

 motion so that they behave like polar nuclei. Consequently it is not uncommon 

 to find three or four nuclei at the middle of the sac where one expects to find 

 the two polar nuclei. In such cases the extra nuclei clearly belong to the 

 synergids or antipodals, these regions showing a corresponding lack. Associated 

 with parthenogenesis in Alchemilla is the phenomenon of polyembryony, the 

 extra embryos coming from the synergids or from the cells of the nucellus. 



c. J. c. 



f 1 



CYTOLOGY, EMBRYOLOGY, 



AND 



MICROSCOPICAL METHODS. 



AGNES M. CLAYPOLE, Throop Polytechnic Institute. 



Separates of Papers and Books on Animal Biology should be sent for Review to Agnes M. Claypole, 



55 S. Marengo Avenue, Pasadena, Cal. 



Holmgren, Niles. Ueber das Verhalten des The materials used were the oviduct, 



Chitins und Epithels zu den unterliegenden , ^ ji^vro >.i 



Gewebearten bei Insecten. Anat. Anz. 20: spermduct and sheath of Sarcophagus 



480-488, 8 figs., 1902. and Musca, and the thoracic muscula- 



Ueber die morphologische Bedeutung des ture of C/^/m/^w/^x larvee. Tissue was 

 Chitins bei den Insecten. Anat. Anz. 21 : 

 373-378, 5 figs., 1902. killed in Perenyi's, Von Rath's, Flem- 



ming's and Carnoy's mixtures and in 

 sublimate (concentrated solution in normal salt). Perenyi, Carnoy and subli- 

 mate gave the best results. Sections were cut 2-3 \x thick and stained 24 hours 

 in 2 per cent, hematoxylin solution after 24 hours preparation in 2 per cent, 

 iron-alum ; Congo red was used as a counterstain. Three kinds of chitin forma- 

 tion were observed. One (vagina of Sarcophagus carnaria) consisted of numer- 

 ous parallel lamellae following in direction the free border of the lining epithe- 

 lial cells. These cells are low cylindrical with moderately large nuclei, poor in 

 chromatin ; the cell bodies are completely filled with parallel fibrils placed at 

 right angles to the layers of chitin. Another type is found in the sperm ducts. 

 The thick layer of chitin is here composed of very many slender chitin columns 

 or threads lying at right angles to the surface and placed on a layer of substance 

 that stains deeply in iron hematoxylin. The matrix cells are low, flat, cylindri- 

 cal epithelium about equal in thickness to the layer of chitin. Nuclei are mod- 

 erately large and rich in chromatin. Apparently the chitin is formed by the 

 chitinization of the free border of the cells themselves, the vertical striae of 

 the epithelium being preserved as chitinous columns. The median oviduct of 

 Musca shows still another kind of formation ; here the chitin has no visible 

 structure and reacts but feebly to stains. The matrix cells are small and 

 spindle-shaped, drawn out to a point toward the lumen of the duct. These 

 points project up through the chitin layer nearly to its surface. The nuclei are 

 moderately large and rich in chromatin ; the cell-bodies are striated with the 

 striae pointing outwards and penetrating into the structureless chitin. In all 

 these cases the chitin is due to the activity of epithelial cells, in the rest it orig- 



