!»Sl SUMMARY 01' CURRENT RESEARCHES RELATING TO 



Branchial Skeleton of Sabella.* — M. II. Vialhmes recommends 

 the maceration of the anterior end of a Sabella in a one-third per 

 cent, solution of alcohol, for the study of its hranehial skeleton. It 

 is composed of a pair of basilar plates, each of which is inclosed in 

 the corresponding hranehial lobes ; each plate is formed of a very 

 thick envelope of connective tissue and a central mass of cartilage ; 

 the latter consists of very large cells with thick walls, closely 

 packed against one anothor and showing no signs of any fundamental 

 substance. In calling this structure cartilage, the author is careful 

 to note that he follows preceding writers, and that he by no means 

 identifies it with what is called cartilage in vertebrates. In the 

 antenna the hypodermis is formed by a layer of cylindrical cells 

 provided with very long vibratile cilia; the cartilaginous axis is in 

 direct contact with the lower surface of the hypodermis by one of its 

 edges, and by the other with a vessel which extends the whole length 

 of the antenna; this vessel is set in a large lymphatic lacuna, which 

 contains also nerves and muscles. The axis is formed by a central 

 set of cartilaginous cells which are invested by a very thick sheath ; 

 this last is very complex in structure. It is best studied after 

 maceration for twenty-four hours in a third per cent, solution of 

 alcohol, staining with picrocarmine, and putting in glycerin ; 

 further study is aided by teasing. The author comes to the conclu- 

 sion that the so-called cartilage resembles in structure the notochord 

 of vertebrates, while its " perichondrium " recalls the fibrous sheath 

 which invests that rod. 



Conodonts.f — As the result of their study of Conodonts, Herrn 

 K. v. Zittel and Dr. J. V. Bohon have been led to conclude that 

 these structures are neither related to the dentine teeth of Selachian 

 or other fishes, the horny teeth of Cyclostomata, the odontophores of 

 Mollusca, the beaks of Cephalopoda, nor the spines of Crustacea, but 

 do in form and structure closely resemble the oral armature of Anne- 

 lids or Gephyrea. If this be true, there must have been in Palaeozoic 

 times an immense number of very varied worm forms. 



Armed Gephyrea or Echmroids.J — Prof, M. Eietsch communicates 

 a detailed memoir on the armed Gophyrea or Echiuroids. His in- 

 vestigations are based on two species of Bonellia, on Thalassema 

 Neptuni and Echiurus Pallasii. 



1. The memoir begins with a detailed historical survey, and 

 with an interesting account of the habits and external characters of 

 these forms. 



2. The integument. — The various Echiurians closely resemble one 

 another in the nature of their integumentary layers. There is a 

 constant occurrence of (1) cutaneous glands, more or less concentrated 

 in the papillae, and sometimes exhibiting highly differentiated struc- 

 ture (Th. erythrogrammon Sluiter). (2) A cutis of var'able thickness 

 including pigment and a ganglionic plexus ; (3) three muscular 



* Ann. Sci. Nat.— Zool., xx. (1886) Art. No. 2, 20 pp., 1 pi. 



t SB. K. Bayer. Acad. Wiss. Miinchen, 1886, pp. 108-36 (2 pis.). 



| Rec. Zool. Suisse, iii. (18S6) pp. 31o-515 (6 pis.). 



