132 Dr. Carl Matzdorff: Jahresbericht über 



ausgeht, sodann eine pelagisch - planktonische und darauf eine 

 peJagiscli - nektonische Stufe annimmt, und aus dieser die Archi- 

 coelomaten herleitet. Von ihnen stammen u. a. die Bryozoen ab. 

 Weiter entwickelten sich aus ihnen andrerseits die Archichordier 

 (Artmotrocha), die ferner den Euchordiern den Ursprung geben, 

 von denen sich seitlich aber auch die Hemi- ( Hdlauof/los.m.'^') und 

 Diplüchordier ableiten. Zur letztgenannten Oruppe gehören die 

 Phoroniden, Cephalodisciden und Rhabdopleuiiden. 



IL Weiter geht Verf. auf die Archichordier unter Bezugnahme 

 auf den Bau von Cephalodiscus dodecalophus ein. Eingehend wird 

 dieses Thier besprochen. Den Schluss bilden ausführliche Diagnosen 

 der Archichordier, ihrer beiden Untergruppen und der drei ge- 

 nannten Familien der letzteren; sie geben ein Bild davon, wie 

 Verf. den Bau dieser Thiere auffasst. 



„Archichorda. Body composed of three archimeric Segments, 

 protomere, mesomeres, and metamere. Ectoderm simple, in great 

 part ciliated and glandulär, secretes mucoid exoskeleton (tube, coe- 

 noecium). Nervous System still in connection with the ectoderm, 

 consisting of central dorsal ganglion, pre-oral ring, post-oral ring, 

 dorsal and ventral cords, and, in addition, a more or less diffuse 

 nervous plexus. Mesoderm in four coelomic pouches, the protocoele 

 and metacoele showing secondary indications of a paired condition. 

 Protocoele opens to exterior, usuall}' by two proboscis-pores; the 

 mesocoeles and collar-pores and the metacoeles have either paired 

 nephridia. functioning as genital ducts, or closed genital ducts. 

 Muscular system prominent in protocoele (the „animal" organ), and 

 in some a circular and longitudinal layer in the metacoeles. A 

 mesodermic skeleton of chondroid tissue- a vascular System of 

 haemocoele Spaces, consisting mainly of subneural sinus (heart) near 

 the dorsal ganglion, dorsal and ventral vessels, and a sinus round 

 the gut. A simple digestion tube, with paired lateral (or early fused 

 into one) notochords, never free from the gut, and one or more 

 pairs of pharyngeal clefts. A subneural gland, opening primarily 

 into stomodaeum, gonads confined to metacoeles. Metamere bears 

 a ventral organ of attachment, ventral sucker. Habitat burrowing 

 or sedentary. 



1. Hemichorda." 



„"2. Diplochorda. Mesomeres produced laterally into a number 

 of ciliated branchial tentacles, which in the adult point upwards 

 in front of the mouth, are supported by a chondroid skeleton, and 

 subserve Ingestion of food. Metameres reduplicated by a dorsal 

 flexure. Stomodaeum with subneural gland still opening to exterior, 

 and extending into the subneural sinus. Paired notochords in pharynx, 

 not displaced forwards. A short Oesophagus, stomach, and intestine. 

 One pair of pharyngeal clefts may {Cephalodiscus) or may not 

 (R/tabdopleura, Phoronis) be present, with chordoid walls. Ventral 

 sucker forming the organ of attachment throughout life. 



(1) Cephalodiscida. Protomere persistent throughout life as 



