756 SUMMARY OF CURRENT RESEARCHES RELATINQ TO 



hero tlicro was regeneration, if tlio nucleus was contained in the injured 

 part, but not otherwise. The processes of regeneration were found to bo 

 cither in the form of a healing of the wound by deposit of carbonate of 

 lime, which was excreted by the surface of the protoplasm, or in the 

 formation of new chambers. There is a similar process of regeneration 

 in Orhitolites temtissima and O. compJanata, but the formation of new 

 chambers was more frequent than in Poli/stomella. 



When we come to ask how it is that there can bo snch a difFerenco 

 in regenerative processes between a Diffhujia and an Orhitolitef, it is 

 obvious that there must be a dittercnce in the shell. This difference 

 appears to lie in its mode of formation. In the former, as in all Mono- 

 thalamia, the shell appears at the moment of division, and is quite perfect 

 after the separation of the newly-formed individual. There are no 

 further changes — that is to say, there is no growth of the shell. Put 

 in terms of the protoplasm, this means that it has no secretory activity, 

 and it is in consequence of this that there is no regeneration of a shell 

 which has been injured or totally removed. 



In the Polythalamia the relations are quite different ; their forms 

 almost certainly reproduce themselves by a kind of spore-formation, 

 although this has not yet been directly observed. It is, however, known 

 that young Polythalamia are to be found as unicamerate Protista in the 

 body of the mother. If these develope into complete Polythalamia a 

 new chamber is formed on the primitive one, to which again another 

 new one is attached, and so on. From this it follows that the Poly- 

 thalamia, so long as they continue to form new chambers, must have the 

 power of secreting tests. A natural consequence of this mode of test- 

 formation in the Polythalamia is the phenomenon that the forms with a 

 relatively small number of chambers, such as Polystomella, have much 

 less power of regeneration than forms with an enormous number of 

 chambers, such as Orhitolites. The capacity for regeneration in the 

 Polythalamia is, therefore, proportional to their capacity for forming 

 new chambers ; the latter, again, marks the extent of development, and 

 the power of regeneration is, therefore, at least continuous with the 

 whole period of development. Dr. Verworn cannot accept the view of 

 Gruber that we ought not to speak of the development of Protozoa, for 

 he sees in the chamber-formation of the Polythalamia a process which 

 is not mere growth, for the chambers do not resemble one another, and 

 the Protist has quite a different appearance when it has only a few 

 chambers from that which it presents when it has many. Eegarding 

 the process as representing a true development, he believes that it may 

 be made useful in determining the phylogenetic relations of some forms 

 of tests. 



It would be of interest to discover whether the capacity for regene- 

 ration diminishes or is lost when new chambers cease to be formed. 

 The influence exerted by the nucleus in the regeneration of the test of 

 Polystomella appears to be of especial importance. Among recent obser- 

 vations on the formation of the nucleus are those which bear on its 

 relation to secretion ; Korschelt observed in the epithelial cells which 

 secrete the chitinous ovarian rays in the eggs of Nepa and Ranatra that 

 the nucleus, at the time of secretion, has a peculiar rhizopodal form, 

 and sends out pseudopodia-like processes to the side in which the chitin 

 is secreted. He further convinced himself that all cells which are 

 known to have branched nuclei have a secretory character. As, however, 



