260 SUMMARY OF CURRENT RESEARCHES RELATrSTQ TO 



chambers secreted and abandoned by the protoi)lasm of Archer's 

 Cklami/domyxa ; and they are of especial interest as giving the first 

 indication of pseudopodia being capable of secreting a membranous 

 investment. With this may bo compared Griiber's statement (see 

 next note) as to the existence of a cuticula-like layer in Amcehce. 



Arclierina is one of the non-nucleate Gymnomyxa, and in respect 

 of its abundant colony-formation reminds us of Microgromia socialis. 



Studies on Amoebae.* — A, Gruber, after descriptions of Amveha 

 villosa Leidy and of the new species A. prima, seciinda, tertia, quarta, 

 quinta, hinncleafa, and lucida, as well as of A. verrucosa and A. proteus, 

 finds that the facts here related show that there are a number of 

 separate and exactly definable Amcehce which do not pass into one 

 another; he has convinced himself of this by observing for months 

 and even years forms living in the same locality. The diagnosis of 

 an Amaha must be based on its average size, the consistency of the 

 protoplasm, and the movements thereby conditioned, as well as on 

 the characters of its contents, such as vacuoles, granules, crystals ; 

 but chiefly on the number, size, and structure of the nuclei. Five of 

 the species described in the present essay are multinuclear, and it is 

 proved how definitely the nuclei are distinguished from one another, 

 and with what certainty one can conclude from external characters 

 on the structure of the nucleus, and vice versa. Thence results the 

 remarkable fact that two very similar species of Amcehce may have 

 very differently formed nuclei, and that in forms which are externally 

 very diflferent the nuclei may be quite similar. In any case the 

 number of the different forms of nuclei is much more important than 

 has hitherto been supposed. 



We cannot as yet form any idea of what are the differences in the 

 protoplasm that are of significance ; the conditions of existence appear 

 to us to be the same for all Amoehoe ; many indeed live in the same 

 places and on the same kinds of food. This resemblance is, however, 

 perhaps not real, and we must believe that natural selection has had 

 the same influence in fixing variations among Amoehoe as with higher 

 animals. Gruber thinks that Carpenter is in error in excluding the 

 Foraminifera from this influence and in referring the development 

 of the cornuspire of OrbitoJites to an internal tendency to variation. 



Though we cannot discover any law in the changes of the amoeba- 

 body, nor explain the causes of the phenomena of adaptation, it is 

 not right to set them aside. The large number of variations among 

 Amcehce show us that protoplasm is a material which can be moulded 

 into an interminable number of forms, and if here the smallest 

 changes in its constitution are seen to be sufficient to form a new 

 species, we can hardly wonder at the variety of adaptations which are 

 seen when cells are compounded into Metazoa. 



Gruber is, further, of opinion that the discrimination of zones of 

 different kinds of protoplasm is due to a misunderstanding ; the 

 amoebic body always consists of a single mass of protoplasm in which 

 the various contents lie suspended ; where the plasma is fluid the 



* Zeitachr. f. Wiss. Zool., xli. (1884) pp. 186-225 (3 pis.). 



