NOTES AND MEMORANDA. ^05 



body from the stem, the solitary condition and the mode of 

 gemmation. 



The specific characters, such as the number of tentacles and 

 tlie presence or absence of the pedal gland, exhibit many modifi- 

 cations in the different kinds. The modifications sometimes 

 take place in individuals of the same species but of different ages. 

 In the bud the arms are fewer in number than in the adult ; 

 sometimes also the pedal gland is present in the bud, but absent 

 in the adult. In fact, some species of Loxosoma seem to be, 

 relatively to others, the same animals, but in different phases of 

 development. For example, L. Neapolitanum, which has few 

 arms and a pedal gland, bears a striking resemblance to one of 

 the early stages in the development of L. Kefersteini, which in 

 the adult state is destitute of the gland, and has a larger number 

 of arms. The author regards L. Neapolitanum, as the primitive 

 species {'' espece originaire"), and thinks that the divergence of 

 the other species has taken place in two different ways — (1) by 

 the disappearance of the pedal gland, and (2) by the multiplica- 

 tion of the tentacles. — T. Hincks. 



Development of Acanthocystis. — In the * Jena Zeitschrift ' 

 Dr. R. Hertwig records that his researches have made known 

 to him three modes of increase in the Heliozoon Acantho- 

 cystis. The simplest is, of course, that by subdivision, 

 already noticed by Greeff. To the author it seems to be a 

 pretty common process, at least he so judges from frequently 

 noticing two nuclei (on treating examples with osmic acid, 

 followed by Beale's fluid) both lying in a common endosarc, 

 seeming to shutout the idea of a previous conjugation of two 

 individuals. He has also noticed two nuclei in Schulze's 

 Actinolophus. But as to the mode of origin of the binu- 

 cleated state, he has no very connected observations to record. 

 He found nuclei the nucleoli of which had become elongate, 

 whilst the nuclear membrane showed an annular constric- 

 tion, showing that the nucleus increases by self-division, as 

 observed by Schulze in Actinolophus. 



A second mode of increase the author had an opportunity 

 of observing in Acanthocystis aculeata. He met with a single 

 example, with which a globe was in connection, having all 

 the appearance of a second individual. This consisted of a 

 granular protoplasm, but free from foreign bodies, nor could 

 there be detected in it either a nucleus or a special endosarc. It 

 lay in a diverticulum of the ' skeleton ' of the Acanthocystis, 

 which was mainly composed of tangential pieces (in A. acu- 

 leata the skeleton consists of two elements — tangentially 

 posed elongate spicules, composing a thick investment, also 



VOL. XVIII. NEW SER. O 



