The above figures were published by Professor Grassi in November 1896, in the Quarterly Journal of Microscopical Science, edited by E. Ray Lankester and published by Churchill & Sons.
Speculations as to the ancestral connection of the great group of vertebrates with other great groups have been varied and ingenious; but most naturalists are now inclined to the view that it is a mistake to assume any such connection in the case of vertebrates of a more definite character than we admit in the case of starfishes, shell-fish, and insects. All these groups are ultimately connected by very simple, remote, and not by proximate ancestors, with one another and with the ancestors of vertebrates.
Fig. 21.
The unicellular parasite Benedenia, from the gut of the common Poulp or Octopus. 1 is the normal male individual; 2 and 3 show stages in the production of spermatozoa on its surface by budding; 4, 5 and 6 show a female parasite with spermatozoa approaching it.
Fig. 22.
Production of spermatozoa on the surface of the unicellular parasite Coccidium oviforme, from the Rabbit’s intestines.