494 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



elusions at which embryologists have arrived respecting the 

 homologies of the various parts of the sexual apparatus in 

 the two sexes so beautifully shown as in the animal under 

 consideration. Did any doubt remain regarding the similar- 

 ity of plan upon which these are built up, it would be at 

 once dispelled by an inspection of the sexual organs of Hy- 

 cena crocuta." The taxonomic deduction may be surmised. 

 Since there is so great a difference between the Hycena cro- 

 cuta and the other species of the family, it would seem that 

 in the interests of an expressive system, the fact that there 

 are such differences should be represented in the nomenclat- 

 ure by distinct generic designations for the forms so differ- 

 ing; and it will be advisable to retain the modified genus 

 Crocuta proposed by the late Dr. Gray for the Hycena cro- 

 cuta, while the other species can be preserved in the restrict- 

 ed genus Hycena. 



The Placental Characteristics of the Sirenians. 



It is probably generally known to our readers that great 

 importance has been attached to the mode and extent of de- 

 velopment of the placenta and contiguous parts in mammals, 

 and that the systematic arrangement of the class has been 

 based on the modifications of these parts by several eminent 

 naturalists. The gaps in our knowledge of the placentation 

 of the class have interfered with the completeness of the tax- 

 onomy, but these have been gradually filled, and during the 

 past year the most serious hiatus has been obliterated by the 

 elucidation of the characteristics of the placenta and embryo 

 of the Sirenians. The Dutch University of Utrecht lately 

 procured the footus of a dugong with its adjacent membranes, 

 and this has been studied by Dr. Paul Harting, and elabo- 

 rately described in the Tijclschrift voor Nederlandsche Dier- 

 kundige Vereeniging. The following is a summary of the 

 results of his observations : 



1. The e^o; of the common du^on^ is an elongated oval 

 sack, of which the greater portion was situated in one of the 

 cornua of the uterus, but a small part of which in the neigh- 

 borhood of the anterior pole penetrated into the other cornu. 



2. With the exception of the two poles and the adjoining 

 area, the entire chorion is covered with very dense but short 

 and little ramified villosities. 



