336 H. B. POLLARD. 



&c., by one end — hundreds together. Apparently they are 

 deposited by preference on fragments of tufa, with the colour 

 of which they match. Kept in aquaria the young fish hatch 

 out at about the twenty-fifth day. Very possibly they grow 

 faster in their natural habitat. I found that the best way to 

 obtain the embryos ready for section-cutting was to snip ofi* 

 the free projecting ends of the egg-shells with scissors, and 

 quickly shake the embryos out into dilute nitric acid or picro- 

 sulphuric acid (Kleinenberg). Afterwards when wanted the 

 embryos may be removed from the yolk in alcohol. I at first 

 employed the methods of Henneguy (6), removing the embryos 

 from the yolk before complete hardening in alcohol, but by 

 these methods they are very liable to be deformed. Sections 

 were made by the Thoma microtome, and usually 5 /z in thick- 

 ness. For convenience I used Kastschenko^s " Beschneider '' 

 (12) in order to obtain good ribbons of sections. The models 

 were made after Strasser's method (23). 



Brain. 



One finds by experience that, in order to understand the 

 disposition of the various organs in the Teleostean embryo, an 

 exact comprehension of the form of the brain at the separate 

 stages is necessary. The development of the brain in the 

 trout has been described by Rabl-Riickhard (19), who investi- 

 gated the embryos as opaque and transparent objects under 

 the microscope. Goronowitsch (4) studied the early stages of 

 the brain in the salmon by means of models. My own ob- 

 servations have been made by models and projections, and 

 though in the main I have but to confirm what Goronowitsch 

 says, yet Gobius shows some not uninteresting variations from 

 the salmon, and, moreover, some description is necessary in 

 order later to explain the disposition of the mesoderm and mouth. 



Fig. 1 represents the brain of Gobius in the first stage 

 viewed from the side. Scarcely any flexure is visible apart 

 from the general curve of the embryo. As shown by trans- 

 verse sections, the extent dorso-ventrally is far greater than 

 from side to side, the former being perhaps ou the average 



