INVERTEBRATE ANIMALS. 103 



in the hollow thorns of an Acacia, and in 

 return protects the tree from the formidable 

 attacks of leaf-cutting ants. The Ecltons, or 

 foraging ants, he regards as being in intelli- 

 gence at the head of all the insect tribe. 

 1[ Male, Female, and Worker of the Hive Bee, 

 British series of Bees, chiefly collected in the 

 neighbourhood of Liverpool, by H. H. H., and 

 deposited by the Liverpool Royal Institution. 



Supplementary Note to Group 11. 



The following Extract is from an address delivered by my fiend 

 Professor Allman, F.R.S., to the Biological section of the British 

 Association, 1873. 



" Let us take an example in whicli these two j)rinciples seem to be 

 illustrated. In rocks of tlie Silurian age there exist in great profusion 

 the remarkable fossils known as Graptolites. These consist of a series 

 of little cups or cells arranged along the sides of a common tube, and 

 the whole fossil presents so close a resemblance to one of the Sertu- 

 larian hydroids which inhabit the waters of our present seas as to 

 justify the suspicion that the GraptoUtes constitute an ancient and long 

 since extinct group of the Hydroida. It is not, however, with the 

 proper cells, or hydrothecfe, of the Sertulariaus that the cells of the 

 Graptolite most closely agree, but i-ather with the little receptacles 

 which in certain Sertularinse belonging to the family of the Plumu- 

 laridae we find associated with the hydrothecse, and which are known 

 as " nematophores." A comparison of structure, then, shows that the 

 Graptolite may, with considerable probability, be regarded as repre- 

 senting a Plumularia in which the hydrothecse had never been 

 developed, and in which their place had been taken by the nemato- 

 phores. 



" Now it can be shown that the nematophores of the living Plumu- 

 laridae are filled with masses of protoplasm which have the power of 

 throwing out pseudopodia, or long processes of their substance, and that 



