236 First Maturation Spindle of AUolobophora Foetida 



Wheeler, William Morton, '97. — The Maturation, Fecondation and Early 

 Cleavage of Myzostoma Glabrum Leuckart. Arch, de Biol., T. XV. 



Wilson, E. B., 'ge-'oo. — The Cell in Development and Inheritance. 



'04. — The Germ-regions in the Egg of Dentalium. The Journ. Exper. 



Zool., Vol. I. 



EXPLANATION OF PLATES. 



All the photographs are of the egg of AUolobophora foetida and were taken 

 by the method described in Zeit. f. wiss. mik., Bd. XVIII, 1901, "A new method 

 of focusing in photo-micrography," Foot and Strobell. 



The Zeiss apo. 2 mm. immers. lens 140 apr. and compensating ocular 4 

 were used, and for the one thousand magnification a camera draw of 25% 

 inches. 



Many of the photographs were taken on the Seed No. 27 and the Agfa Isolar 

 plates. With these rapid plates an exposure of only one to three minutes was 

 required even on cloudy days. In the photographs of Plates VII, VIII and IX 

 the wider area of accurate focus demanded by the subjects made it necessary 

 to close the substage diaphragm to a point requiring doubling the time of 

 exposure. 



Only a small part of each section is reproduced, except in photos. 68 and 69. 



The reproductions of Plates I, IV and VI are by the half-tone process, and 

 Plates II, III, V, VII, VIII and IX are by the Rotograph process. 



PLATE I. 



The oocytes shown in Photos. 1 to 11 inclusive were fixed in platino-osmic 

 (Hermann's fiuid without acetic acid) and stained with iron haematoxylin fol- 

 lowed by dilute Bismarck brown. All the sections are 2i/^^. 



Photo. 1. X 1000. First of four consecutive sections of a germinal vesi- 

 cle of an oocyte first order from a receptaculum ovorum, showing chromatic 

 filaments stained black, and faintly stained nucleoplasm. 



Photo. 2. x 1000. Next section to above. 



Photo. 3. x 1000. Next section to Photo. 2 showing an accessory nucleo- 

 lus stained black like the chromatic filaments. This is the only accessory 

 nucleolus in this germinal vesicle. 



Photo. 4. X 1000. Next section to above showing the principal nucleolus 

 which stained yellow by the Bismarck brown. This nucleolus is also present 

 in the two following sections. 



Photo. 5. X 1000. Section of a germinal vesicle of an oocyte first order 

 from the receptaculum ovorum, showing black chromatic filaments, and 

 large yellow nucleolus with small black granules (these granules are lost 

 in some of the reproductions). This section was first photographed unstained 

 and the granules in the nucleolus were as black and sharply differentiated as 

 in the stained preparation. 



Photo. 6. X 1000. First of four serial sections of a germinal vesicle of 

 an oocyte first order from receptaculum ovorum showing black chromatic fila- 

 ments and one accessory nucleolus, also stained black. 



Photo. 7. x 1000. Second section from above showing the principal 

 nucleolus. This nucleolus stained brownish yellow and is present in the two 

 following sections. 



