46 C. M. CHILD AND E. V. M. McKIE. 



two optic pigment cups are symmetrically situated but lie closer 

 together than in normal animals and are united by a continuous 

 band of pigment. 



In Fig. 7 a transverse section of the nervous system from about 

 the posterior fourth of the preocular region is shown. It consists 

 of a single fiber tract surrounded by cells and without any trace 

 of division into right and left halves. Comparison with Fig. 3 

 which is from about the same level in the normal animal shows 

 a marked difference in form. Fig. 8 shows the- level of the eye-. 

 The difference between this and Fig. 4 from the normal animal 

 is striking. In Fig. 8 the fiber tract is partially divided into 

 right and left halves, but the two parts are close together instead 

 of being widely separated and connected by a long commissure 

 as in Fig. 4. In Fig. 9 a section at the level of the auricles is 

 drawn : much the same differences from the normal (Fig. 5) ap- 

 pear here. The two ganglionic masses are closely connected, 

 while in the normal animal they are widely separated. 



The figures from this teratophthalmic head show one other 

 point of interest. The individual from which the sections were 

 made was much smaller than the full grown animal of Figs. 2-5. 

 Figs. 2-5 and 7-9 are drawn to the same scale and comparison 

 shows at once that the ganglia arc almost as large in the tera- 

 tophthalmic as in the normal animal . This is a general character- 

 istic of physiologically younger as compared with older and of 

 smaller as compared with larger animals. In the small young 

 animal the nervous system is always of relatively large size and in 

 small animals which result from the regulation of pieces the 

 same is true, except in the more extreme abnormal types, where 

 the nervous system is often small. Thus as regards the develop- 

 ment of the nervous system as well as its rate of metabolism 

 during development (Child, 'i \b) the animal formed by regulation 

 resembles a young animal. 



In oilier teratophthalmic individuals with partially tused eyes 

 the general form of the ganglia was found to be murh the same 

 as in the case described and the degree of fusion or separation 

 of the ganglia corresponds rather closely with thedegreeof fusion 

 or separation of the eyes. In these forms then the eye- serve 

 to some extent as an index of the condition of the nervous -\ stem. 



