169] LIFE HISTORY OP GORDIUS AND PARAGORDIUS—MA 7 49 



color had begun to appear over the rest of the cuticula at the two ends, 

 but the middle region of the body was still white. The specimen was kept 

 alive until July 26, when it was attacked by fungi and had to be killed. 

 It had been mated and had laid some eggs, and had been kept in an open 

 glass dish in the window where the sun shone on it part of the day; but the 

 color had not noticeably changed except that the white had become soiled. 



Hypoderm. The hypoderm in this species develops very much as in Gordius 

 rohustus. The cells at first are flattened, very early become columnar, and 

 after the completion of the adult cuticula become flattened again over 

 most of the surface of the body. They remain higher at the two ends. At 

 the anterior end, under the white surface, they project far into the interior, 

 becoming rod-shaped or almost fibrous in nature. The nuclei remain in 

 the outer halves of the cells while the lower parts become clear and form a 

 distinct mass just anterior to the supraesophageal ganglion. These hyaline 

 bases of the cells later disintegrate or else form a substance that is dissolved 

 during the preparation of the mount (Figs. 153, 154). 



Protoplasmic connections between the hypoderm cells are present in 

 this species as in the previous one but no canal system has been found. 

 The cells are in cross section more easily distinguishable than in Gordius 

 robustus. 



The nuclei from the first are more distinct than in Gordius robustus 

 and each consists of a large central nucleolus surrounded by an achromatic 

 sphere and a somewhat indefinite membrane (Figs. 165,170). Later the 

 membranes become more distinct, but the nuclei do not become so definite- 

 ly outlined as in Gordius robustus and the fusion of chromatic spheres 

 occurs only in very few instances. During the formationof the adult 

 cuticula the chromatic substance increases in quantity and becomes scat- 

 tered thruout the nucleus (Fig. 167). In the adult stage the nucleus 

 shrinks and the chromatic substance forms one or two discs, almost com- 

 pletely filling the membrane. 



Nervous system This system is built on the same fundamental principle 

 as in the previous species, but while some parts stand out clearer, the struc 

 ture of the others is not so easily brought out. 



Central nervous system. The brain in this species also appears in 

 the posterior part of the proboscis, but does not begin its development 

 until even later than in Gordius robustus. The rudiment of the brain 

 appears as a group of deeper staining cells around the connecting strand 

 between the stylets and the base of the proboscis (Fig. 162) but the 

 cells soon lose their staining properties and become indistinguishable from 

 the mesoderm cells which surround them (Fig. 151). The bundles of 

 nerve fibres leading from them can, however, be distinguished. Even at 

 a much later stage, when the nerve cord is beginning to separate from 

 the hypoderm, the gangHon cells are difficult to distinguish from the rest. 



