262 Miscellaneous. 



specimens, iu which, moreover, the lower extremity of the body- 

 cavity is open ; but it is entirely wanting in the well-preserved 

 individuals described. In the latter the lower extremity of the 

 body-cavity, which is divided into 12 chambers, is closed by a 

 distinct floor, which surrounds the anus, and is divided by the 12 

 septa into the same number of segments. In each of these segments, 

 in Fenja, there is an exceedingly fine oval aperture, partly covered 

 by a fold ; both the floor and the aperture are clothed with epithe- 

 lium. Here, consequently, there can be no question of tearing 

 away. 



" As regards JEgir, here also the described animals were quite un- 

 injured. Some specimens were torn by the dredge, but could be 

 distinguished from the uninjured ones without any difficulty. In 

 Mgir the body-cavity is! likewise divided into 12 chambers by 12 

 septa, which reach to the floor, where they are firmly attached, and 

 which they consequently divide iuto 12 segments surrounding the 

 anus. At the lower end of the rectum in this animal there are 

 fissures through which the chambers of the body-cavity communi- 

 cate with the rectum. These fissures do not extend to the anus, 

 but terminate some millimetres above it and are clothed with 

 epithelium. During the observation of living animals I frequently 

 saw tolerably long, solid masses of excrement discharged from the 

 anus, after which the aperture contracted again. In jEgir conse- 

 quently there can be no question of mutilation." — Sitzungsber. Gesell- 

 schaft Naturf. Freunde zu Berlin, 1889> pp. 55 and 99. 



On the Anatomy and Developmental History of Petromyzon Planeri. 

 By M. K. Nestler. 



Investigations upon Petromyzon Planeri made by the author in 

 Prof. Leuckart's laboratory have revealed some interesting facts, 

 especially with regard to the development of the definitive oesophagus 

 during the metamorphosis. Dr. Schneider, in his " Contributions 

 to the Comparative Anatomy and Developmental History of the 

 Yertebrata," states that the oesophagus is produced as a new 

 formation, an invagination originating from the anterior extremity of 

 the intestinal fold, continuing forwards the mesenterial fold of the 

 stomach, and running into the dorsal margin of the branchial 

 cavity. Although at first hollow, this soon becomes solid, and then 

 extends, as a solid cellular cord, to the velum. The latter thus 

 furnishes not only the epithelium, but also the mucous membrane 

 and musculature of the oesophagus. 



The author's investigations led to different results. The oesophagus 

 really originates as a solid cord, but its cells furnish only the epithelium 

 of the definitive oesophagus, the central cell-material being absorbed ; 

 the musculature originates from the surrounding connective tissue. 



