368 THE AMERICAN NATURALIST. | (Vor. XXXIX. 
cannot be had by almost any institution in the country, however 
remote from the coast. Fish properly packed, so as to secure 
coolness and freedom from too great pressure, will endure well 
several days' transportation, especially in the cooler seasons of 
the year. Skates which are intended for injecting for non-his- 
tological purposes are not injured by freezing, provided that they 
are not exposed to alternate freezing and thawing. 
A point of minor importance is the fact that it is easier to 
secure good preservation of skates than of dogfish. The flat- 
tening of the skate's body facilitates the penetration of the pre- 
serving fluid to the deep organs. Furthermore, to get sexually 
mature animals, it is necessary to use dogfish of such large size 
that the preservation and storing of material for a large class 
become a serious problem. The same number of small sexually 
mature skates makes a much less bulky mass of material. 
The objection that the skate is a highly specialized elasmo- 
branch does not apply, to any great extent, to its internal anat- 
omy. The specialization involves chiefly the general form of 
the body. The skeleton and muscles are the systems most 
affected. The remaining organs undergo relatively unimpor- 
tant changes in position incident to the flattening of the body. 
In their essential morphological characters and relations they 
are closely comparable to those of the shark-like elasmobranchs. 
From a practical point of view, it might be said that the special- 
ization of the skate is in the direction of ee for labora- 
tory purposes. 
The plan which has been followed for several years pastin the 
laboratory of vertebrate comparative anatomy at Harvard Uni- 
versity seems to me to be an excellent one. The student first 
makes a general dissection of the dogfish, exclusive of the 
blood vessels, then injects a fresh skate for the study of the 
circulatory system. By this arrangement he becomes familiar 
with the anatomy of the more primitive elasmobranch and 
studies a typical elasmobranch circulatory system under condi- 
tions far more favorable than those offered by the dogfish. At 
the same time, his familiarity with the dogfish enables him to 
detect the essential elasmobranch characteristics i in the skate and 
to comprehend the nature of its specialization. Thus, he is 
