128 PROCEEDINGS OF SOCIETIES. 



the Protozoa through the Infusoria, and succeeding groups 

 to the Arthropoda, whilst a similar gradation is trace- 

 able from the Sponges, through Ccelenterata to the Mollusca. 

 The break, however, is very great between Sponges and 

 Ccelenterata. No hypothesis is involved in this: it is simply 

 a matter of fact. The probability of genetic relations Pro- 

 fessor Huxley did not propose to discuss. 



Lecture II. — The Foraminifera were considered in this lec- 

 ture. They may be placed as a gi'oup among the Monerozoa, 

 containing, as they do, some of the very simplest forms of 

 life. One of the simplest of Foraminifers is Gromia — a 

 jelly-like mass, with extensive pseudopodia enclosed in a 

 small horny shell. Some Foraminifers have more or less 

 calcareous matter in place of this horn ; and in Carpenteria, 

 a very remarkable encrusting form, siliceous spicula exist, 

 leading on thus to the Sponges. Some Foraminifera have 

 an arenaceous shell, built up of particles of foreign matter 

 cemented together, instead of an excreted one, and the 

 arenaceous species exactly repeat in many cases the forms of 

 the calcareous ones. By the aggregation of a number of 

 simple chambers, such as that of Gromia or Orbulma, a great 

 variety of forms may be produced; and it is in this way that 

 many of the simpler Foraminifers are constructed. If the 

 chambers grow one out of the other so as to leave a space 

 between the adjacent walls of succeeding chambers, we get the 

 interstitial canals of such genera as Operculina. If in addition 

 to this the chambers completely enclose their j)redecessors 

 as they develop — leaving at the same time an interval 

 between the adjacent walls — we get the complicated structure 

 of Nummulina. It is found that the most distinct-looking 

 forms of Foraminifera — helicoid, globular, cylindrical, &c. — 

 run into one another by completely gradated series, and 

 hence the old classification of them by the form of aggrega- 

 tion has been abandoned. Carpenter, Parker, and Rupert 

 Jones have shown the impossibility of drawing such fine 

 distinctions, and in some cases have demonstrated that fifteen 

 genera of D'Orbigny are but varieties of a single " species^' 

 or type. The group is now divided, first, into Imperforata 

 and Perforata, according as the shell-structure is whole or 

 perforated by minute canals, through which the sarcode sub- 

 stance of the animal passes in every direction. The Imper- 

 forata includes three families : the Gromida, the Milio/ida, 

 and the Lituolida. The Perforata also presents three families : 

 the Lagenida, the Globigerinida, and the Nummulinida. The 

 Gromida, all have a membranous or horny shell ; the Millio- 

 lida have a porcellanous calcareous shell ; the Lituolida repeat 

 the Milliolida forms, but in arenaceous instead of calcareous 



