374 ON THE ANATOMY OF AMPHIOXUS LANCEOLATUS. 



Eetzius describes the spinal marrow as terminating consider- 

 ably behind the anterior extremity of the chorda dorsalis, in 

 a brain exhibiting scarcely any dilatation. He perceived a 

 dark point which he supposed might be the rudiment of an 

 eye, but he could observe no cerebral nerves. He saw 

 numerous ribs, but no branchial clefts, and described a large 

 opening at the posterior extremity of the gill-cavity, which 

 he supposed to be a branchial opening similar to those in 

 the myxine. 



Midler's own observations were made upon Mr. Yarrell's 

 specimen, and also upon two sent to him by Eetzius. He 

 verified Eetzius's and Sandevall's account of the chorda dorsalis, 

 on the sheath of which he perceived circular fibres. The 

 oral filaments he described as consisting of central and tegu- 

 mentary portions. The black spot or rudiment of an eye he 

 could not detect. He observed the general structure of the 

 branchial cavity, ribs, and vessels, but did not determine 

 the existence of the branchial aperture described by Eetzius. 

 He states that the intestine terminates anteriorly in a cul-de- 

 sac, a little behind which the branchial cavity opens into it 

 on the left side. He supposed that some glandular streaks on 

 the wall of the cul-de-sac of the intestine represented the 

 liver, and considered a row of glandular masses on each side, 

 consisting of cells containing dusky oval bodies as the ovaries. 

 After some remarks on the structure of the muscles and skin 

 of the Lancelet, Professor Miiller states the . necessity for 

 further observations to ascertain the details of its structure. 



The only specimens of the Lancelet, then, which have 

 been examined are Pallas's specimen, Mr. Couch's two speci- 

 mens, one of which is in the possession of Mr. Yarrell, the 

 specimens examined by Eetzius, Sandevall, and Midler, and 

 the two in my own collection. Two specimens, I believe, 

 exist in the Museum of the Zoological Society of London.* 



' ;; Magazine of Natural History, .Inly 1838. 



