Miscellaneous. 83 



3. Segmentation is completed in about two hours, and gives rise 

 to a gastrula, with ectoderm, endoderm, digestive cavity and blas- 

 topore, and a circlet of cilia or velum. At this stage of develop- 

 ment the embryos crowd to the surface of the water and form a 

 dense layer less than | inch thick. 



4. The blastopore closes up ; the endoderm separates entirely 

 from the ectoderm; and the two valves of the shell are formed, 

 separate from each other, at the edges of the furrow formed by the 

 closure of the blastopore. 



5. The digestive cavity enlarges and becomes ciliated; and the 

 mouth pushes in as an invagination of the ectoderm at a point 

 directly opposite that which the blastopore had occupied. The 

 anus makes its appearance close to the mouth. 



6. The embryos scatter to various depths, and swim by the action 

 of the cilia of the velum. The shells grow down over the digestive 

 tract and velum; and the embryo assumes a form so similar to 

 various, marine Lamellibranch embryos which are captured by the 

 dip-net at the surface of the ocean that it is not possible to identify 

 them as oysters without tracing them from the egg. The oldest 

 ones which I succeeded in raising in aquaria were almost exactly 

 like the embryos of Cardium figured by Loven. 



7. The ovaries of oysters less than 1| inch in length, and pro- 

 bably not more than one year old, were fertilized with semen from 

 males of the same size, and developed normally. 



An illustrated paper on the embryology of the oyster, with a 

 detailed account of my observations, will be published, shortly, in 

 the Eeport of the Maryland Fish Commission for 1879. — Amer. 

 Journ. Sci. and Arts, December 1879, pp. 425-427. 



Observations on the Salivary Glands of the Echidnas. 

 By M. H. VlALLANES. 



From the anatomical arrangement of the different glandular 

 masses which produce the saliva we may distinguish in the Echidna 

 the three groups of glands which are met with in most Mammalia, 

 namely : — 1, the parotid glands ; 2, the submaxillary glands ; 

 3, the sublingual glands. 



The parotid glands, which are so constant in the Mammalia, 

 escaped the notice of Cuvier and It. Owen ; the latter even formally 

 denies their existence. I have found the parotids well developed 

 in the Echidna ; but instead of being situated in front of the 

 auditory passage, they are situated far back, at the middle of the 

 neck. 



in tbe Echidna there are on each side two submaxillary glands- 

 one deep-seated, the other superficial. The deep-seated submaxil- 

 lary gland has been well described by Cuvier and Owen. Its ex- 

 cretory duct passes directly forward, and pierces the great transverse 

 muscle which forms the superficial layer of the flour of the mouth. 



