File:The pedigree of man - and other essays (1903) (14762380224).jpg

Identifier: pedigreeofmanoth00haec (find matches)
Title: The pedigree of man : and other essays
Year: 1903 (1900s)
Authors: Haeckel, Ernst Heinrich Philipp August, 1834-1919
Subjects: Man Evolution Man Evolution
Publisher: London : A and H.B. Bonner
Contributing Library: ASC - York University Libraries
Digitizing Sponsor: York University - University of Toronto Libraries

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Fig. 3. The same, seen from below : the lower half has been removed.a. Sense-vesicles (eyes and ears) on the margin; t. Tenta-cles ; b. Oral tentacles ; v. Cavity of the stomach ; ov. Ovaryin the lower wall of the last; gv. Branching radiatingcanals, running from stomach to margin and there combin-ing in a circular vessel. The division of animals to which the Aurelia andits allies, the jelly-fish, belong, bears the name of Hy-dromedusae. To the same group belong the Hydroid- THE DIVISION OF LABOR. 103 polyps, altogether dissimilar from the free-swimmingjelly-fish in external aspect, attached to the sea-bottom,or sedentary on seaweed. A solitary little animal, be-longing to this group, the small fresh-water polyp orhydra (Fig. 4), lives, and is widely distributed, in ourponds and ditches. This elegant little creature is foundvery frequently on the under aspect of duckweed orthe leaves of the water-lily. In the contracted state
Text Appearing After Image:
Fig. 4. (Fig. 4 to the left) it is a green or orange-red littlemass, the size of a pins head. Extended (Fig. 4 to theright) it is a thin thread, an inch in length. By oneend it is firmly fixed. At the other is the mouth, sur-rounded by a circle of from four to eight tentacles.The mouth in this case leads into a simple gastriccavity. Our fresh-water polyp reproduces itself in 104 THE DIVISION OF LABOR. the simplest fashion. Either by eggs or by budding, itis ever producing creatures like itself. But in the sealive many hydroid polyps, scarcely distinguishablefrom the fresh-water one, but nevertheless reproducingthemselves in a manner very remarkable and verydifferent, i.e. in connexion with the Medusae justdescribed. For from the eggs of the Medusae other Medusae donot arise, but hydraf orm polyps, and these latter pro-duce by gemmation not polyps but Medusae again.Hence in these Hydromedusae the daughter does notresemble the mother, but the grandmother. The firstgeneration is like the

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