362 
little to say since it fails to develop. I have never seen any indication of 
bloodvessels, either in the embryo or in the yolk so far as these could be 
made out by circlulating blood. There is now and then an embryo that 
shows what seems. from surface view, a little lakelet of blood. No corpus- 
cles, however, can be seen, and I think they are only accumulations of a 
pigment of scme sort. Nevertheless a considerable portion of the yolk sub- 
stance is absorbed. This is transferred to the embryo by probably the same 
method as is employed prior to the development of the vascular system. 
The body of the embryo is always much too short and appears heavy. 
The tail may develop to a considerable length, and in the more successful 
individuals may show the caudal fin-folds with fine radiations. The body 
lacks regularity of form and outline. Muscle segments develop, plainly 
marked off by the brown pigment deposits along their borders. The muscle 
segments are active, shown by the frequent movements of the tail. 
The eyes may be developed to varying degrees, or in many embryos 
there is no indication of an eye. A quite Common condition is the appear- 
ance of only a single eye. Some of the embryos show an accumulation of 
pigment cells either in two patches or one, which because of their location 
and the fact that they are in rather well-circumscribed patches, probably 
represent the eye. Two eyes are formed in many. These are always located 
far forward, so that they seem set into the anterior surface of the head. 
These may be quite large, well pigmented and showing a lens, or they may 
be smaller, varying to a condition where merely two small pigment areas 
are located on the very extreme anterior tip of the pointed head. 
The ear vesicle is usually formed. In the place where the vesicle should 
be there is commonly formed, in the older embryos, an enlarged vesicular 
structure. This. in some cases, is beyond doubt the enlarged ear vesicle. 
The embryos gradually die, but the better formed ones have lived for me 
for ten days after the normals had hatched. 
Fundulus heteroclitus, female, 
x 
Tautogolabrus adspersus, male. 
This cross was made five times. The percentage of impregnation may 
be almost normal, as shown in experiment 36 in the following table: 
Experiment 28b...... APO noe ee 65 per cent. 
~ 34b.... eas oe pa i (alate 
a [ng SAPs Sle 8 ee ie) I tO ale ads 
dy 1O2DS s:c0 eso paar eamnwnenelenl cde Soy ere 
