ZOOLOGY. 367 



development in the ovary. Prof. Agassiz was informed by the fisherman 

 who had supplied him with the specimens in which this discovery was made, 

 that he had for a long time supposed that the young were formed in the 

 parent. 



Prof. Agassiz had been endeavoring to find homologies of development in 

 all animals of the vertebrated type, and had succeeded in tracing them so far 

 as to be able to distinguish between vertebrata and invertebrata in the 

 earliest stages of development of the egg. 



The President remarked that every new instance of ovarian impregnation 

 was of great importance. The most recent researches go to prove that the 

 seminal fiuid comes in direct contact with the ovum, and perhaps enters into 

 its substance ; but in Anableps, the ovurn is surrounded by a membrane 

 which would tend to prevent any such entrance. 



Prof. Agassiz observed that he considered fecundation as a series of acts 

 rather than a single act. In Chelonians, the circumstances under which the 

 eggs are developed, would lead to the inference that an impulse is first 

 received from the male, and then that four successive copulations in four suc- 

 cessive years, twice a year, are necessary before segmentation takes place in 

 the egg. In the haddock, ovarian gestation has this physiological import, 

 that it shows that what is a normal condition in one animal of a certain type, 

 may be abnormal, and occur only exceptionally hi another animal of the 

 same type, as in man and other of the higher forms of vertebrata. 



DISTRIBUTION OF AMERICAN TURTLES. 



At a recent meeting of the Boston Society of Natural History, Prof. Agassiz 

 stated, that he had been engaged in an investigation into the Geographical 

 distribution of the Turtles of this country. For a correct determination of 

 specific differences, it became necessary to collect specimens from all parts of 

 the country as extensively as possible, and he thinks he has obtained speci- 

 mens of nearly all the species existing in North America, and that he has 

 been able to trace their geographical distribution very completely. The 

 results to which he has arrived show this fact, that several species which have 

 been supposed identical throughout their whole geographical range, are 

 now demonstrated to be really distinct ; whilst others which have been de- 

 scribed as difierent species, the young alone in some instances having served 

 for description, have been found to be one and the same. He particularly 

 called attention to the danger of describing species solely on theoretical 

 grounds as different because they inhabit difierent parts of the world, or as 

 identical from general resemblances. Dumeril and Bibron in their work on 

 Herpetology, and others, have attempted to identify marine turtles of differ- 

 ent waters without sufficient authority. Prof. Agassiz had taken particular 

 pains to enquire about the Sphagis or Leather-backed Turtle, which is found 

 from the West Indies, northward, and which has been taken at Cape Cod. 

 This animal has been said to inhabit the Mediterranean, but after a thorough 

 investigation he can find only seven or eight instances recorded of its 

 having been found there. The museum at Salem furnishes an opportunity for 

 distinguishing between the Imbricata of the West Indies and that of the 



