No. 6. — The Development of Penilia schmackeri Richard. 
By Mervin T. Sudler, Baltimore, Md. 
With three plates. 
During June, 1896, immense swarms of small crustaceans sud¬ 
denly appeared in the water of the harbor of Beaufort, N. C. 
Their numbers were so great that the animals usually found near 
the surface of the water were completely obscured and, in towing, 
the meshes of the net after being drawn through the water a few 
yards were clogged with these crustaceans. This abundance 
lasted but a few days when the creatures disappeared completely 
and as suddenly as they had appeared. Dr. C. P. Sigerfoos, then 
of the marine laboratory of the Johns Hopkins university, pre¬ 
served a number for future study. 
Three methods were used to preserve and fix these animals ; 
viz.: — 
1. A saturated solution of corrosive sublimate used cold for a 
few minutes. 
2. A corrosive sublimate and acetic acid reagent, composed of 
Corrosive sublimate (saturated solution) . . 90 parts 
Glacial acetic acid . . . . . . 10 “ 
3. 80% alcoholic picro-sulphuric acid. 
The animals were washed in water after treatment with each of 
these solutions, run up through the graded series of alcohol until 
they were in 80%, and kept until used. The material so preserved 
was placed in my hands and was studied b}^ means of sections of 
the adults containing young and the separate embryos after they 
had been remoAmd and by means of adults and embryos mounted 
whole. Klein enberg’s haematoxylin as a staining agent gave the 
best results in the first case, and where they were mounted whole a 
few moments staining in Czokor’s alum cochineal proved the most 
satisfactory. Xylol was used as a clearing agent and Canada balsam 
as a mounting medium. 
Systematic Position. 
The crustaceans were found to be Cladocera (Daphnoidea) and 
belong to Penilia, of which two species have been described by 
