Note 22 — Chapter IV · THE MORPHOLOGICAL COMPOSITION OF ANIMALS.

Since this was written in 1865 there has come to light evidence more completely to the point than any at that time known. In the subdivision of Platyhelminthes known as Turbellaria, there are some, the Microstomida which, by a process of segmentation form “chains of 4, then 8, then 16, and sometimes even 32 individuals.” “Each forms a mouth [lateral] and for some time the chain persists, but the individuals ultimately become sexually matured and then separate.” (Shipley, Zoology of the Invertebrata, p. 92.) Here it should be remarked that the lateral mouths enable the members of a string to feed separately, and that nutrition not being interfered with they doubtless gain some advantage by temporary maintenance of their union—probably in creeping.