468 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



that it is to be regarded as the remnant of the pharynx of Trematoda. 

 They seem to him rather to support the older suggestion that the ros- 

 tellum is to be homologised with the proboscis of Turbellaria. He 

 points especially to developmental resemblances between it and the pro- 

 boscis of the Turbellarian Macrorhynchus. 



Incertae Sedis. 



Development of Phoronis buskii.* — Dr. A. T. Masterman finds that 

 in this species the mesoblast appears to arise from five separate parts of 

 the archenteric hypoblast, one of these being unpaired and pre-oral, the 

 other four paired and post-oral. The first arises as a hollow outgrowth 

 of the archenteron, its cavity being shut off from the archenteron in the 

 course of development. Of the post-oral somites, the first (collar 

 somites) arise as solid masses of cells, which at first have no cavity ; 

 the second (trunk somites) appear to arise in the same way at the anal 

 extremity, though it is possible that they are originally hollow out- 

 growths with the walls in contact. In origin and in details of develop- 

 ment, there is close correspondence with Balanoglossus, thus confirming 

 the author's view of the existence of relationship between Phoronis and 

 Balanoglossus. 



Affinities of Phoronidea."]* — Prof. L. Eoule has already argued that 

 there are important resemblances between the development of Phoronidea 

 and that of Chordata. He goes on to indicate the resemblances between 

 the early stages of Phoronidea and Nemertea. The pilidium is certainly 

 not homologous with the actinotrocha, but there are some striking re- 

 semblances in developmental procedure. So the young Phoronid, before 

 it has assumed the actinotrocha disguise, resembles the Annelid trocho- 

 phore in the origin of the germinal layers, e.g. origin of the primary 

 mesenchyme. For the stage succeeding the gastrula, Roule proposes 

 the term vermula ; it may, in a sense, be called the common form from 

 which the more specialised trochophore, pilidium, and actinotrocha are 

 derived. 



Budding in Ectoproctous Bryozoa.J — Dr. Fr. Ladewig has studied 

 this especially in Bugula avicularia, and with the following results. 

 The rudiment of the polypid is always an invagination of the ectoderm. 

 From a slight incurving, to start with, the process is traced to the appear- 

 ance of a distinct lumen of invagination. The avicularia' rudiment is 

 an ectodermic evagination, formed about the same time as the first differ- 

 entiation of tentacles in the associated polypid. In the evagination a 

 distal club-shaped portion is differentiated, into the lumen of which 

 there wander mesenchyme cells from the body-cavity of the mother- 

 zooecium ; this part becomes constricted off from the head of the avicu- 

 laria. On the distal side of the evagination there is formed an inva- 

 gination of the outer germinal layer, similar to that in the rudiment of 

 the polypid bud. The musculature of the avicularia arises from the 

 mesoderm, which is established by the multiplication of the mesenchyme 

 cells to form a connected endothelium. The invagination itself forms the 



* Quart. .Tourn. Micr. Sci., xl'iii. (1900) pp. 375-418 (4 pis.). 



t Comptes Kendus, cxxx. (1900) pp. 927-30. 



X Zeitschr. wiss. Zool., lxvii. (1900) pp. 323-39 (1 pi.). 



