The Process of Heredity 529 



pure drawn on hatching. The head diameter of this M pure was 

 1.8 mm., as compared with 1.3 mm. for the H pure. Two more 

 H hybrids had hatched since the last examination, but were dead 

 when noticed. Both specimens were pale, twisted and emaciated. 



At 23 days: About thirty more M pures hatched. Nearly all 

 of the rest were dead, many of them having reached almost the 

 maximum size before dying. 



At 27 days: All embryos of the series except about thirty H 

 hybrids and about sixty M hybrids, were dead.. The H hybrids 

 show^ed a wider range of developmental stages and abnormal con- 

 ditions than the M hybrids. The latter were a fairly healthy 

 looking lot, seemingly quite normal except for the presence of the 

 large yolk mass attached to them. Some of them, when liberated 

 by dissecting off the egg membrane, swam about quite actively 

 and continued to live for several days in sea-water, although 

 handicapped by the presence of their abnormally large yolk sacs 

 full of a kind of material that they seem utterly unable to assimilate. 

 I tried to free them from their encumbrance by pricking the sac and 

 liberating the excess yolk, but the specimens thus operated soon 

 died, probably from loss of blood, since some blood was seen to 

 escape when the yolk material issued from the sac. A number of 

 the M hybrid embryos, liberated artificially from the egg mem- 

 brane, lived for as long as four days, but during this time the yolk 

 mass did not diminish and the embryos probably starved. A 

 typical specimen of these artificially liberated embryos was quieted 

 and drawn (Plate V, Fig. m). 



All of the H hybrids were dissected out of their membranes and 

 presented a bizarre collection of freaks. A number of the types 

 shown were drawn and will be seen in Figs. 3 to 8 inclusive. Fig. 

 3 presents the type most nearly normal. Fig. 4 is an unusual 

 type, showing an enormous growth of pectoral fins, which seem to 

 have continued to grow although the rest of the body had ceased to 

 increase in size. This might be explained by the fact that the 

 only noticeable circulation in the whole specimen was in these fins. 

 Figs. 5, 6 and 7 show various degrees of a common type, in which 

 the trunk region was greatly reduced. Fig. 8 shows a rare type, 

 in which the head region was ill developed, although the trunk was 



