438 SUMIIAUV OF CURRENT RESEARCUliS RELA.TINQ TO 



componiul Ascidians, there is no Rogmcntation cavity, and tlio gas- 

 trulii is l\)i-nie(I by cpiboly. The first colls of the organs arc not all 

 formed by the scgnieutatiou of the yolk, but by free ccll-forniation in 

 its midst. The endoderm in the larva forms the epithelium of the 

 branchial cavity, of the peribranchial cavities, and of the intestine, as 

 well as the notochord. The mesoderm is formed by free cell-forma- 

 tion from the primitive endoderm, and gives rise to the body of the 

 eudostyle, among other organs. 



The systematic position of Amaroecium seems to be between the 

 compound Ascidians with stolons, such as Pcrophora, and the more 

 ditl'ereutiatcd colonies which have a common cloaca, like Botrylius, 

 and which arc the most degraded of all the Ascidians. 



B, FolyzDa. 



Morphology of the Bryozoa.* — Dr. W. J. Vigelius has examined 

 the Bryozoa material collected during the cruise of the ' Willc-m 

 Barents,' and has studied the mori)hology of Flusfra niemhranaceo- 

 truncctta Smith, and Barcnfsia bidbosa Hincks. The results are now 

 published in one of the most complete monographs that has yet 

 appeared on any division of the Bryozoa. 



Much space is devoted to the individual value of the polypide. 

 Grant, Milne-Edwards, and Ehrenberg considered that an individuura 

 was composed of the zocecium and polypide ; but on the other 

 hand, Allman, Smith, Eeichert, and Nitschc considered these as 

 separate individuals. This has more recently been disputed by 

 Ecpiachoif, Hatschek, Salensky, and Kohlwey ; and now Dr. Vigelius 

 brings forward a series of arguments to show that the " cystide " and 

 " polypide " should together be considered as an individuum, and the 

 ovicells and radicular appendages he only places as organs, whereas 

 the entire aviculariura is an individual corresponding with the 

 zooacial individual. With Salensky he considers the crown (Kelch) 

 of the Pedicclliua not as the ecjuivalent of a polypide, but as the 

 homologue of a polypo-cystide of which the stalk is an integral part, 

 and he would thus deal with the structure of Barentsia. He unites 

 both the cndocyst and the endosarc under the name parenchym-tissue, 

 as he holds them both as difierentiations of the same tissue. The 

 endosarc he, however, calls " Stranggewebe." Out of this parenchym 

 the muscles take their origin, and, in opposition to the views of Joliet, 

 the parietal muscle is formed after the intestine, and can remain after 

 the a1 sorption of the latter, and this is also the case with the opercular 

 muscles. 



The sexual organs can be formed cither from the " Stranggewebe " 

 or the parietal layer of the imrenchym. The ovarium may be found in 

 very young zooecia even before the tentacles are formed. Herma- 

 phrodite individuals with both ripe ova and male organs were only 

 very seldom found, and it is very seldom that both sexual products 

 are ripe at the same time. 



* Bijdr. tot do Dii.rkuiulo, xi. (1884) 104 pp. (S pis.). 



