64 FAMILY GROMIDA. 



Adinoplirys in the Radiolarian. A detailed account of its very simple organization and of its 

 mode of life (so far as at present known) having been already given (^ 32), there is no occa- 

 sion here to repeat the description ; but it may be advantageous to point out that the origin 

 of the whole ramification of pseudopodial expansions from a single stem which is limited by 

 a definite envelope, shows Lieberkuhnia to be strictly conformable to the imperforate type. 

 From no other part of the body are pseudopodia given off, as would be the case if it had any 

 affinity to the perforated series. 



Genus II.— Gromia (Plate III, fig. 2). 



78. The genus Gromia was first constituted by M. Dujardin in 1835 (xxxv) for the 

 reception of a group of Khizopods characterised by the possession of a brownish-yellow, soft, 

 membranous, ovoidal or spheroidal " test," having a small round orifice, whence issue very 

 long pseudopodia, which ramify and become much attenuated towards their extremities. In 

 the membranous nature of its " test" Gromia resembles Arcella and Eii(jlyplia, but the character 

 of the animal entirely differentiates it ; and it thus holds in the Reticulose series a rank exactly 

 parallel to that oi Arcella in the Lobose, and oi Enr/li/jjlia in the Radiolarian. This genus has 

 since been especially studied by Schlumberger (xcix a); and still more recently by Professor 

 Schultze (xcvii), whose account of it is in some respects more complete than that of 

 Dujardin, but corresponds with his in all essential points. 



79. The smooth, coloured "test" of Gromia, which commonly attains a diameter of 

 from 1-lOth to l-12th of an inch, looks to the naked eye very much like the egg of a Zoophyte 

 or the seed of some aquatic Plant ; and its real nature would not be suspected until, after an 

 interval of rest, the animal begins to creep about by means of its pseudopodia, and to mount 

 along the sides of the glass vessel that contains it. Some Gromia are marine, and are found 

 among tufts of Corallines, Ccramiacise, and other Alga3 ; whilst others inhabit fresh water, 

 and adhere to Ceratophylla, Confervae, and other plants of running streams. Various species 

 have been described, differing slightly in the size, form, and colour of the " test," and in the 

 proportional length of the pseudopodia ; but, with the evidence we have of the variability of 

 all such characters in other instances, these specific distinctions cannot be regarded as having 

 any valid claim to acceptance. The composition of the " test" has been studied by Schultze 

 (xcvii, p. 21), who states that it resists the action of boiling solutions of the caustic alkalies, 

 and that of the concentrated mineral acids, even sulphuric. With sugar and sulphuric 

 acid it gives a red colour ; whilst by iodine and sulphuric acid it is turned to a 

 blackish hue, with a tinge of violet. The organic substance which it seems most to 

 resemble in these reactions is cellulose, but it differs from cellulose in not being dissolved 

 by sulphuric acid ; and it would seem to have some relation to cJiitine and the 

 substance of the Iiorni/ tissues. Of the animal of Gromia, and of its mode of obtaining its 

 food, a sufficient account has already been given (^^ 33, 34) ; and it has only to be here 

 stated in addition, that the shell has no permanent attachment, but that the animal moves 

 slowly from place to place by the alternate extension and contraction of the pseudopodia which 



