93G SUMMARY OF CURRENT RESEARCHES RELATING TO 



Molluscoida. 

 ;3. Bi'yozoa. 



Movements of Polypides in Zocecia of Bryozoa.* — Dr. J. JulUcn 

 has n note on the protrusion and return of the polypido in the zocecia of 

 monoderni chcilostoniatous Bryozoa. He points out that, when a poly- 

 pido wishes to emerge from its cell it must yield its place to a quantity 

 of water of equivalent volume. But the zooecium is rigid. The opera- 

 tion is effected, as the author has seen in a specimen of Cafcmcella 

 veiitrtcosa, by the posterior edge of the operculum. This operculum is 

 articulated laterally, and while it closes the tentacular sheath anteriorly 

 it closes posteriorly a second cavity, which is the pouch into wliich the 

 sea water penetrates when the polypide emerges. In SchizoporeUa the 

 operculum has a small tooth on its lower lip ; this is lowered wlieu the 

 polypide is being protruded, and keeps the orifice of the water-chamber 

 widely open. When the polypide returns to its cell the water is driven 

 out, and the operculum is closed over the whole orifice, which, therefore, 

 is not ouly the opening of the tentacular sheath, but also that of the 

 compensatory water-chamber. 



Ontogeny of Marine Bryozoa.|— Dr. W, J. Vigelius finds that his 

 observations corroborate in many important particulars the work of 

 M. J. Barrois. The form of the young sessile primary animal is at 

 first more or less rounded, but later becomes elongated, and has some- 

 what the form of the sole of the foot. Longitudinal sections show that 

 the development of the nutrient apparatus commences with an invagina- 

 tion of the aborally placed disc-organ. The cells which form this 

 invagination are considerably elongated, and lie in a single layer which, 

 later on, forms the epithelium of the enteric canal. Around this invagina- 

 tion there arises later a second cell-layer which is made up of much smaller 

 flattened cells. The author believes that this layer arises, in Bugula 

 calatlius, from the mesodermal larval tissue. He has never, like 

 Ostroumofi", found any rudiment of hypoblast taking part in the forma- 

 tion of the bud. The number of spines is inconstant in the primary 

 animal, and the buds always arise terminally. 



Cristatella mucedo.^ — Dr. J. JuUien finds that the male organs of 

 this Bryozoon arc formed of seminiferous vesicles, or male ovules or 

 mother-vesicles, in which the spermatozoa are developed ; they are 

 suspended to the intracolonial trabeculte. He declares that the colonial 

 disc is not a true foot, and that the direction taken by it may be in its 

 long or in its broad axis. On twenty-five regular lophophores he 

 counted from 71 to 80 tentacles, and on nine irregular lophophores from 

 3 to 70. 



Delagia Chaetopteri. § — Prof. J. Joyeux-Laflfuie gives a full account 

 of this interesting new Bryozoon, the preliminary notice of which we 

 have already recorded. |1 Part of the colony may be fixed on the inner 

 wall of the tube, and the rest placed more deeply, though aways near 

 the inner wall. The zocecia are oval, flattened along the plane of the 



* Bull. Soc. Zool. France, xiii. (1888) pp. 67-8. 



t Mr. Zool. Stat. Neapel, viii. (1888) pp. 374-6 (1 pi.). 



X Bull. Soc. Zool. France, xiii. (1888) pp. 165-6. 



§ Arch. Zool. Expe'r. et Gen., vi. (1888) pp. 135-51 (1 pi.)- 



11 See this Journal, 1888, p. 403. 



