216 University of California Publications in Zoology [Vol. 19 



in a fixed matrix, denser and more refractive than the cytoplasmic 

 hyaloplasm. In the resting state these are arranged peripherally just 

 within the membrane. The nucleus is usually disc-shaped, being flat- 

 tened anteroposteriorly. It is, when seen from the front or rear, round, 

 oval, or irregularly elongated. In the living state, and when intra- 

 vitam stains, such as neutral red and Bismarck brown, are used, there 

 is at the center a karyosome which seems at times to consist of closely 

 compacted granules surrounded by a light hyaline area of nuclear sap 

 in which there are no granules, the periphery of which seems usually 

 to be bounded by a membrane. When the nucleus disintegrates this 

 granular karyosome persists for from fifteen to thirty minutes. "When 

 stained with iron-alum haematoxylin, Delafield's haematoxylin, phos- 

 photungstic haematoxylin and others, this karyosome appears homo- 

 geneous and this whole mass to be surrounded by the hyaline area, thus 

 giving a perfect vesicular nucleus. 



As to the reticular nature of its protoplasm, I am inclined to 

 regard the surface of the vacuoles as modified, perhaps by stress or 

 strain, into thickenings or longitudinal strings of plasmosomes, the 

 interstices of the larger vacuoles being filled with still larger granules 

 of various kinds, food, mitochondria, plastids, metaplastic granules, 

 and foreign organic and inorganic bodies. There is little or no circu- 

 lation of vacuoles or protoplasm visible in Collodictyon. That the 

 nuclear protoplasm has the power to create and absorb or eliminate a 

 membrane, metabolic in character, around the microkaryosome, will 

 be described as a prophase phemonenon ; even so, a cytoplasmic vacuole 

 may be bounded by a definite membrane, kinetic in character, which 

 may be modified so as to appear reticular when stained, and on which 

 are accumulated small granules, either scattered or in long, bead-like 

 strings. All of this is in addition to the other granules which may be 

 held in the interstices of both large and small vacuoles. 



The physical nature of the protoplasm of Collodictyon, therefore, 

 appears to be a fluid, which may be modified by metabolic, kinetic and 

 other life processes into granular or reticular variations, these how- 

 ever, being subject to reabsorption into a hyaline fluid, or becoming 

 by-products, such as plastids, never again functioning in metabolism 

 or life processes, though still retained in the cytoplasm. 



Besides the protoplasmic vacuoles, other kinds may be present. 

 1. Food vacuoles, which may contain plants or animals just engulfed, 

 or which may be very old and alkaline in reaction, simply water or 

 digestive spaces in which little remains. These may flow together 



