458 Miscellaneous. 



Note on the Carotids of Rhea americana. By Frakklen P. Evaks, 



Esq., University College, Bristol. 



In dissecting a young but almost full-grown specimen of Rhea 

 americana I find that the right carotid is evidently present, though 

 it is much smaller (about ^ inch diam.) than the left. Its position 

 for some distance past its origin corresponds to that of the left 

 carotid ; but subsequently, instead of converging to meet the latter, 

 which runs along the hypapophysial canal, it continues onwards by 

 the side of the right pneumogastric nerve and jugular vein. As 

 the late Mr. A. H. Garrod, in his paper on the carotid arteries of 

 birds (P. Z. S. 1873, p. 470), states that normally the left carotid 

 alone is present in this species, it is possible that this difference is 

 due to age ; if so, it is interesting to find that a structure, the absence 

 of which in the adult bird is regarded by Mr. Garrod as of sub- 

 family importance, is originally present in the young bird, persist- 

 ing even until close upon sexual maturity. Perhaps this may 

 explain the conflicting statements of Prof. Owen with regard to 

 the anatomy of Apteryx as quoted by Mr. Garrod. 



On the Origin of Alternation of Generations in Uydro-Medusce. 



By W. K. Brooks. 



It is hardly possible that the form of development which we now 

 find in most of the hydro-medusiB can bear any close resemblance 

 to their primitive life-history ; and there are many reasons for 

 believing that alternation of generations has gradually arisen through 

 the modification of " metamorphosis/' 



In Cunina we seem to have the ancestral form of development, a 

 direct metamorphosis without alternation. The interesting and re- 

 markable life-history of Cunina was first described by Prof. John 

 McCrady, w r ho found inside the bell of a hydro-medusa, Turritopsis, 

 at Charleston, S. C, a number of hydra-like larvce attached by short 

 tentacles to the subumbrella, and furnished with a xery long and 

 flexible proboscis, with the oral opening at its tip. These larvae are 

 parasitic ; and they obtain their food by inserting the proboscis into 

 the mouth of the Turritopsis, and thus sucking from its stomach the 

 food which it contains. In his first paper upon the subject Prof. 

 McCrady stated his belief that these larvse were the young of the 

 TurritojJSts, which carries its young inside its umbrella and nourishes 

 them with partially digested food from its own stomach. Although 

 McCrady soon corrected this error, and showed that they are not 



net 



error without his correction, and refers to this instance of parasitism 

 as a case of maternal care for the young among the Ccelenterata. 



During the past summer both Turritopsis and Cunina were ex- 

 tremely abundant at Beaufort, N. C, throughout July and August, 

 and I was fortunately able to trace the life historv of each of them. 



