354 



is a spherical bag, inside which the formation and development of 

 the new organs is rapidly progressing * . Instead therefore of under- 

 going no metamorphosis, the young Daphnia only assumes the well- 

 known characters of the genus after the first changes of skin. The 

 author proceeds to compare this phenomenon with a similar one 

 observed by Mr. Spence Bate in Gammarus, by Prof. Huxley in 

 Mysis, by Dr. Cohn in Sphferoplea, in many Annelids, and in the 

 interesting entozoon Monostomum mutabile. The young Daphnia at- 

 tains a length of "025 inch before it leaves the receptacle of the mother, 

 but the length of time during which it remains therein varies ac- 

 cording to the temperature. The author has never met with an ex- 

 ception to the rule noticed by preceding writers, that unisexuality is 

 characteristic of an agamic brood. 



It follows from these observations, that the self-fertile Daphnise 

 are certainly true females, and that the reproductive bodies more 

 nearly resemble eggs than gemmae in their origin and development. 

 Hereafter, however, it may be convenient to give a separate name to 

 those egg-like bodies, which are fertile without impregnation, but for 

 the present they must be called eggs. 



The author then gives a list of the instances of Parthenogenesis 

 which, so far as he knows, are recorded among the Articulata. 

 Finally, he expresses the belief that the careful consideration of these 

 cases, and of the facts now recorded as to Daphnia, and the still more 

 wonderful observations recently detailed by Siebold in regard to Apis 

 (if these latter are confirmed), must surely remove all lingering doubts 

 as to the identity between eggs and buds ; and remarks, that if Prof. 

 Huxley's definition of "individual" and "zooid" is to be adopted, 

 it will be impossible to assert of any Daphnia or Moth, whether it is 

 the one or the other, and the hive-bee will have to be considered as 

 an hermaphrodite, a species without male individuals. 



Under these circumstances, the author suggests that it would be 

 more convenient to continue, as heretofore, to call the individual of 

 any species that which is individualized, even though in this case the 

 individuals of one species will not always be homologous with those 

 of another. 



* It is worthy of notice, that the back fold indicating the divisions between the 

 head and body is opposite the line between the mandibles and the first pair of 

 maxillae, which latter appear therefore to belong to the body, as Zaddach also 

 asserts, and not to the head. 



