326 



Mr. E. Ray Lankester on 



Hackel's Monera as Nuda and the Foraminifera as Testacea) ; 

 2. Nucleifera (embracing Amcehoidea, Gregarrnida, and Catal- 

 lacta) ] 3. Radiolaria or Cytopliora (embracing the Heliozoa 

 or freshwater Radiolaria, and the Radiolaria proper or marine 

 forms); 4. Infusoria (embracing the Suctoria and Ciliata^ 

 excluding the so-called Flagellate Infusoria, which, it seems, 

 should be referred to the Volvocinean Algas) ; 5. Noctilucida 

 {Noctiluca and Peridinium) . 



We are indebted to Hackel's monograph in the ' Jenaische 

 Zeitschrift' (and translated in 'Quart. Journ. Micr. Sci.' for 

 1869) for the knowledge of the Monera and their reproduction. 

 Prof. Ed. van Beneden, of Li^ge, has given a valuable account 

 of the development and structure of a Gregarina from the 

 lobster (Quart. Journ. Micr. Sci. 1870 & 1871), from which it 

 appears that the reproductive spheroid appears iirst as a cytode^ 

 and subsequently acquires a nucleolus and nucleus, whilst 

 considerable tissue-differentiation also goes on, though the uni- 

 cellular condition is maintained. The high differentiation of 

 the Ciliate Infusoria is thus no evidence against their unicellular 

 character. 



The development of the Radiolaria is not properly known in 

 any case. Hiickel, in his great monograph, and more recently 

 Cienkowski (Schultze's Archiv, 1871, and Quart. Journ. Micr. 

 Sci., Oct. 1871) have given some account of the formation of 

 spores, which demonstrate the central capsule to be reproductive 

 like the nucleus in other groups. If the yellow cells should 

 prove to be parasitic, as Cienkowski suggests, then, as in 

 colonies oi Monera or Catallncta,a\l the units, with the exception 

 of the central reproductive body, would be of coordinate value. 



B. The reproductive sphe- 

 roid is at first a nucleated 

 particle of protoplasm ; in 

 some cases it develops from 

 a non-nucleated stage. In 

 many cases the nucleus dis- 

 appears before fertilization. 

 Division of the spheroid then 

 gives rise to a polyplast. By 

 the growth of this pol3^plast 

 either a hollow sphere boun- 

 ded by a single layer of cells 

 is produced, into which a 



portion of its own wall be- ^7 ? ^ j i, • • x- ^ 



^ . • 1 . 1 J Plannla formed by invagination of a 



comes mvagmated or tucked, ^^rt of the wall of a pdyplast with 

 as by the adjustment of a central cavity. (Optical section.) 



Fig. 4. 



end 



