352 



PLATE V 



Fig. 1, a-c. Eggs of SpJuerechinus granulans Lam. 



Fig. 1, a. Thin section (about 1 to 2 yn), passing slightly obliquely to the axis 

 of division, through the so-called attraction sphere of an egg which was 

 in the act of dividing in two. In the centre is the centrosome, which 

 seems to consist of three closely apposed vesicular granules. Picro- 

 sulphuric acid, Delafield's hsematoxylin, damar. 



Fig. 1, J. Thin section through the surface of a similar ovum, showing very 

 plainly the alveolar layer {alv), and the honeycombed structure of the 

 protoplasm lying beneath it. 



Fig. 1, c. Striated protoplasm during division from an entire ovum in pro- 

 cess of division, which was investigated in water after treatment with 

 pioro-sulphuric acid. 



Fig. 2, a-h. ThalassicoUa nucleata Hxl. Section through the central 

 capsule. Osmic acid, Canada balsam. 2, a, part of the intracapsular 

 protoplasm with two vaciioles or albumen spheres. 2, 6, part of the 

 superficial, radially striated intracapsular protoplasm, bordering on an 

 albumen sphere, x about 3100. 



Fig. 3. Hinder end of a living Ohilomonas paramcecium Ehb. Both the 

 alveolar layer {alv) and the honeycombed endoplasm are very distinct. 

 In the latter lie the large amylum granules {am), p, pellicle. 



Fig. 4. Optical section of the marginal portion of a drop of oil-foam prepared 

 from olive oil and NaCl, with a very distinct and relatively high alveolar 

 layer {all)). Seibert yV> ^ 1250. 



Fig. 5. Foam prepared from olive oil and cane sugar. A small part of the 

 meshwork, projected with the camera lucida. x 1200. 



