520 SDMMARY OF CURRENT RESEARCHES RELATING TO 



outer integument, but also at times beneath tbe walls of the oscular 

 tube ; tlie sjiecies are not incrusting, and have a delicate stalk, while 

 the horny fibres are tubes of spongiolin, arranged in dendritic fashion, 

 Z). rosea is found at Port Philip, as is also D. aerophoha. An elaborated 

 and careful account is given of the external and histological characters 

 of these forms. 



The paper concludes with a tabular review of the most important 

 characters of the Aplysillince, which with the Aphjsinince, are the two 

 sub-families of the Aplysinidse ; the former contains the two genera 

 Aplijsilla, with three species, and Dendrilla, with the two described 

 for the first time in this paper. 



Protozoa. 



Characters of Infusoria.* — G. Entz commences with an account 

 of Actinobolus radians of Stein, which was placed by its discoverer in 

 the family Euchelinae ; the investigations of the present author lead 

 him to the discussion of the question of the genetic relationships 

 between that family and the Acinetinas, and as to which are the 

 earlier. If we regard Actinoholiis as an Encheline, the tentacles of 

 which are lately acquired structures which, as more highly difieren- 

 tiated organs, form the sucking-tubes of the Acinetinae, and if we 

 regard this change as going hand-in-hand with the loss of mouth and 

 arms and the greater loss of the cilia, we may consider that the 

 Enchelina3 are the older forms, and Actinobolus intermediate between 

 the two. It would seem, however, that any discussion of this point 

 will be more or less barren till we can come to some more definite 

 idea as to the genealogy of the Ciliata ; we find, that is, that R. 

 Hertwig confidently regards the primitive Ciliate as having been a 

 unicellular organism, which was provided with a continuous invest- 

 ment of cilia, while Bergh looks upon the Peritricha as being the 

 oldest Ciliata, which have been derived from the Cilioflagellata by the 

 reduction of the flagellum and the diiferentiation of a cystostome and 

 cystopyge. 



Mesodinium acarus and Didinium nasutum are closely compared 

 with Urocentrum turbo, with the object of showing that the two 

 former difier so much from the third in all essential points that it is 

 not possible to place all three in tbe same category. The author is 

 of opinion that there are several characters which are as, if not more, 

 important than the ciliation ; such are the absence or presence of a 

 mouth, and in the latter case the characters of the peristome, the 

 structure of the pharynx, the position of the anus and of the contractile 

 vacuole. A study of the ciliation alone will certainly lead to many 

 Infusoria being placed in wrong families. 



The author finds himself compelled to separate the CyclodineaB 

 from the Peritricha, and to regard them as nothing more than 

 EncheliufB in which the ciliation has become confined to two circlets 

 of cilia. It is suggested, but by no means asserted, that the " proboscis " 

 of D. nasutum is a colossal suctorial tentacle. Some points in favour 

 of the iihylogcuctic views of Bergh are noted, but no definite opinion 



* Zcitschr. f. Wiss. Zool., xxxviii (1883) pp. 167-80 (I pi.). 



