358 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Allopora rosacea Greef, and A. subviolacea W. S. Kent. An enquiry into 

 the geographical distribution leads to the conclusion that the origin of 

 the phenomenon of bipolarity is due to the splitting up of widely 

 distributed parent-species by biophysically determined variation. 



Symbiosis in Hydroids.* — H. C. Mtiller makes a note on symbiotic 

 algae found by him in various hydroids in the Bay of Naples, especially 

 in Sertularella pohjzonias L., Aglaophenia pluma L., and Pachycordyh 

 fusca, a species discovered by him. In the last named form symbiotic 

 algas were found in the endoderm throughout the whole hydrocaulus. 

 These zooxanthellae are not distinguishable in appearance from those of 

 other animals. They occur in such numbers that the soft white plasma 

 of the hydroid is coloured yellow or brown. They are never found in 

 the egg-cells of Pachycordyh fusca, so that infection of each new genera- 

 tion must take place. The investigator gives an interesting account of 

 the movements of the xanthellae outside of the animal tissue. 



Alcyonarian with Simple Tentacles. f — Gilbert C. Bourne describes 

 Acrossota liposchra g. et sp. n. from British Xew Guinea, unique among 

 Alcyonarians in having simple digitiform tentacles without pinnules. 

 It requires a new family among the Stolonifera, in close juxtaposition to 

 Cornularidas and Clavularidae. The translucent zooids occur at intervals 

 on a simple sparingly branched radiciform adherent stolon. There was 

 no trace of spicules. The tentacles are eight in number, and the 

 structure of the polyp, in almost all respects except the absence of 

 pinnules and spicules, presents characteristic Alcyonarian features. 



Protozoa. 



Structure and Division of the Amoeba Nucleus. $ — Th. v. "Wasie- 

 lewski and Alfred Kiihn have made a study of the structure and division 

 of the nucleus of the Amoeba. They find that the nucleus consists of 

 an " outer nucleus " and a central corpuscle, which are morphologically 

 independent. The outer portion contains the chromatin of the nucleus. 

 In the resting-nucleus the chromatin substance forms an alveolar layer 

 round the central corpuscle, and during division is transformed into a 

 series of chromatin threads disposed in an equatorial plate. The 

 daughter plates arise by stretching and constriction of the nuclear 

 threads, and the daughter plates, by the dissolution of the threads, 

 form the outer nuclear mass of the daughter nuclei arise. The central 

 corpuscle has no chromatin ; it contains, perhaps constantly, a central 

 granule (centriole ?) ; on division its mass yields the polar bodies and 

 the spindle of the central corpuscle. At the end of the division process 

 the remains of the spindle and the polar bodies fuse to become the 

 daughter central corpuscles. The central corpuscle may therefore be 

 regarded as the division apparatus of the nucleus. In Vahlkampfla 

 mutabilis sp. n. the outer nucleus layer always contains a chromatin body 



* Zool. Jahrb., Abth. Syst., xxxvii. (1914) pp. 267-82. 



t Quart. Jouru. Micr. Sci., lx. (1914) pp. 261-72 (1 pi.). 



j Zool. Jahrb., Abth. Auat., xxxviii. (1914) pp. 253-326 (3 pis. and 8 figs.). 



