30i PllOP. ALLMAN ON SIAIPLE SAKCOUli ORGANISMS. 



In the first state the body has usually the form of a pear, attached 

 by its narrow end to a long cylindrical stem. It is very con- 

 tractile, however, and may assume a spherical or an egg-shaped 

 form. No external membrane or definite cortical layer can be 

 detected. In its interior there is always a very excentric nucleus 

 enclosing a very large nucleolus. In the centre of the wide part 

 of the animal lies a dark spherical body, whose true nature has 

 not been ascertained. Its position generally corresponds to the 

 point in which the pseudopodia if prolonged inwardly would meet ; 

 and Schulze thinks that in some cases he could trace fine lines 

 from it to the pseudopodia. In some specimens there occurred, 

 besides the ordinary granules, numerous orange-red corpuscles, 

 which, along with large nutriment -pellets, lay near the periphery. 

 No pulsatory vacuole was found*. 



The pseudopodia occur only on the more distal part of the body, 

 from which they radiate in all directions. The appearances are in 

 favour of the pseudopodia being composed of a central firm axis and 

 an investing cortical layer ; but on this point the author cannot 

 speak decidedly. A complete withdrawal of the pseudopodia was 

 never seen, the contraction of these processes being at a definite 

 distance from the surface of the body suddenly stopped, as if by the 

 presence of a thick perfectly hyaline investment, which the author 

 thinks is really present in the form of a gelatinous excretion from 

 the body, but which, fi-om its extreme transparency, is all but 

 invisible. In this state the pseudopodia present the appearance 

 of fine lines tipped each with a little granular mass of sarcode, and 

 the Actinolophus closely resembles a Podojphrya. 



The stem is cylindrical, hyaline, and appears to be encased in a 

 delicate sheath. In its interior may be seen several parallel, 

 straight, longitudinal lines. 



Besides the individuals so formed, others occur with a manifest 

 outer envelope. This shows itself at first as a gelatinous invest- 

 ment, so transparent as to be recognized only by its boundary 

 contour. It is traversed by the pseudopodia and by the fine 

 parallel lines from the interior of the stem. In a stage further 

 advanced, a layer of very delicate strongly refringent plates has 

 formed on the surface of the gelatinous mantle, and is continued 

 downwards over the stem. The plates appear to be composed of 

 silica, and ultimately acquire a tolerably regular hexagonal form, 

 but never come so close as to touch one another by their edges. 



* F. E. Schulze, " Bhizopodenstudien," Arch. f. micr. Anat. vol. x. 1874. 



