148 CHARLES R. STOCKARD 



to swim in a perfect fashion. Veiy probably the best of these 

 specimens would present various ill effects from their early arrest 

 could they be kept and observed throughout a longer life period. 

 There are only a few simple performances to be observed in the 

 actions of a newly hatched fish. Whether they are later capable 

 of feeding and digesting food, reproducing, and performing other 

 functions in a normal fashion is unknown for such individuals. 

 The probable later effects as well as the classification of the de- 

 formities following stoppage at various developmental moments 

 will be more fully considered in the subsequent sections. 



One other similar series of experiments may be briefly recorded 

 to further make clear the results which follow various degrees 

 of interference with the rate of development during its early 

 stages. A careful consideration of these records also brings out 

 some of the differences between the effects of completely stopping 

 and of slowing to a decided degree. The significance of the very 

 varied types of deformities which result from early interrup- 

 tions will be considered in connection with the records in the 

 following sections of the discussion. 



Experiment 902, B, C series. Three hours after fertilization, when 

 in the 2-cell stage, eggs were placed in the refrigerator in the following 

 arrangement: Bi and Ci at 5°C., B2 at 7°C., and B3 at 9°C., with a 

 control from the same groups of eggs kept at room temperature. 



When 24 hours old, the control were all developing in a perfect man- 

 ner, but again somewhat slower than the maximum midsummer rate. 

 The germ-caps had flattened on the yolk, but there was neither germ- 

 ring nor embrj^onic shield formation yet visible. The Bi and Ci lots 

 had all divided once or twice before cooling down to the 5°C. tempera- 

 ture. Every egg in both vessels was alive and in the 2-, 4-, or 8-cell 

 stage. In the Ci lot almost all were 8 cells. In many the 8 cells 

 were arranged into two groups of four (fig. 9). 



Lot B2 were, as a rule, in the same condition, all eggs being alive, 

 the great majority in the 8-cell stage, with a few showing the 4-cell 

 stage. 



The B3 lot, after 24 hours at 9°C., were practically all developing 

 at a very slow rate and had reached about the 64- or 128-cell stage. 

 They seemed normal and in good condition other than for their very 

 slow progress. 



Forty-six hours after fertilization, the control showed every egg 

 developing, the germ-ring having grown almost completely over the 

 yolk-sphere, the embryonic body was well formed, but the optic out- 

 pushing had not yet arisen. 



