DEVELOPMENT OF COPIDOSOMA GELECHI/E. 343 



becomes greatly shrunken during the process of fixation, and 

 which in sections appears as a precipitated substance (Fig. 19 A, 

 P.M.}. As to the origin of these different substances we know 

 nothing, but their subsequent history is clear. For the sake of 

 clearness in description we shall use the following terms: (i) l$u- 

 deated Membrane for the outer zone; (2) Granular Layer for the 

 protoplasm containing the embryonic nuclei ; and (3) Precipitated 

 Material for the shrunken fluid-like substance. 



(b) The Nucleated Membrane. In these young polygerms the 

 outer zone stains more deeply than the central mass. The 

 "polar nuclei" have no definite arrangement, but are irregularly 

 scattered throughout the protoplasm. The entire zone therefore 

 is in every sense of the word a syncytium. As the polygerm 

 grows in size the nuclei become arranged into a single layer, 

 and the protoplasm thins out, thus forming a true nucleated 

 membrane about the central or embryonic portion of the egg 

 (Fig. 21, N.M.). In the later history of the polygerm some of 

 the nuclei are clearly surrounded by cell walls, that is, there is a 

 tendency for the membrane to become cellular. 



At first the young polygerms are naked, that is there are no 

 elements from the host tissue laid down on the outer surface 

 of the nucleated membrane. Later a few mesenchyme cells are 

 found on the surface of the membrane, and still later these cells 

 give rise to the adipose tissue (Fig. 22, A.T.}, which may com- 

 pletely surround the polygerm. 



(c) Precipitated Material. This material occupies the central 

 portion of the polygerm. Apparently it is formed through the 

 action of the fixing reagent upon the fluid-like protoplasm. In 

 sections it is very much shrunken, thus leaving an irregular clear 

 space (Fig. 21, C). As we shall see later, it persists throughout 

 the entire polygerm phase of development. 



(d) The Granular Protoplasm and the Embryonic Nuclei. In 

 Fig. 19 the condition of the embryonic nuclei and their surround- 

 ing granular protoplasm is especially clear. Most of the nuclei 

 are indifferently scattered in the protoplasm, but some of them 

 are collecting into groups. The number of nuclei in each group 

 is variable; some groups contain only two or three nuclei, while 

 others may have as many as ten or twelve. The granular pro- 



