396 Charles R. Stoekard. 
2 METHOD AND MATERIAL 
In all former experiments on the developing lens, except 
those which the writer recorded (’09), mechanical methods have 
been resorted to in destroying the early optic vesicle. This has 
been accomplished by burning the region with hot needles or by 
cutting away the tissue. It matters not how cleverly such 
experiments may be performed they are often open to objection, 
particularly when the experimenter has to remove or injure the 
overlying ectoderm in order to reach and extirpate the optic 
vesicle. 
The present experiments have been conducted in an entirely 
different manner. When developing fish embryos, Fundulus 
heteroclitus, are treated with certain magnesium salts, alcohol, 
chloretone or other anesthetic agents, the development of the 
optic vesicles is prevented entirely in some cases, while in other 
specimens only one vesicle forms on either the right or left side, 
and finally a large majority of the embryos present the eyclopean 
defect with a more or less double ventro-median eye. We have 
here, therefore, an exceptidal opportunity to study the relation- 
ship between the development of an optic vesicle and a lens. In 
the first case, does a lens or do lenses ever occur in the eyeless 
specimens? Does a lens ever appear on the eyeless side in the 
single-eyed monsters? Finally do lenses ever arise in their usual 
lateral positions when the embryo has a ventro-median cyclopean 
eye? Allof these propositions are affirmatively answered without 
an operation to injure in any way the ectoderm or tissues in the 
primary lens-forming region. It may be thought that the action 
of the chemical or anesthetic is as severe as an operation but 
this is probably not true, as the embryos after being treated for 
the necessary time with magnesium, on being returned to sea- 
water develop, hatch and swim actively about, living in aquaria 
as long as I have tried to keep them, more than one month. 
The experiments of the past summer have convinced the writer 
that his former idea that the eye defects are due to the anesthetic 
properties of magnesium is correct; and there is no reason for 
believing that certain tissues usually between the eyes are entirely 
