REJUVENESCENCE IN NATURE. 159 



tirely absorbed into the gelatinous envelope.* In Gonium, 

 Folvox, Pandorina, and a plant similarly formed of eight 

 closely connected cells, which perhaps is Kiitzing's 

 Botryocystis Morum, each cell likewise possesses two 

 cilia, which, issuing from the internal body of the cell, 

 project through the gelatinous envelope, and set the 

 whole family in motion by their vibrations. 



The absence of a proper cell-membrane in the new- 

 born gonidia of the Algae is placed still further beyond 

 doubt, when their origin and birth is closely observed. 

 We will examine both somewhat more closely in Ulothrix 

 and (Edoffonium. In Ulothrix, as above mentioned 

 (p. 149), the cells of the filament undergo many divisions, 

 but always in the same direction, at right angles to the 

 longitudinal axis of the filament (horizontal division). 

 As soon as the division is completed, the contents may 

 be separated from the newly-formed wall by acids or 

 tincture of iodine, which proves that such a separation is 



* The genus Gleeococcus exhibits the following characters : ovate, green 

 cells, with a colourless point, from which a reversed funnel-shaped, lighter 

 space extends inwards, together with a largish vesicle at the posterior 

 extremity. Multiplication by simple or double, in the last case decussating 

 halving, after which the cells remain loosely connected together by secretion 

 of soft, gelatinous confluent coats, forming globular, and, finally, amorphous 

 families. The cells of all the generations succeeding each other during the 

 formation of these families (excepting the transitory cells in the case of 

 double halving), are provided with two very long persistent cilia, which only 

 disappear when division commences. The cells exhibit a feeble motion inside 

 the enveloping and connecting jelly, the anterior end jerking in and out, or 

 suddenly retracting a little. The last generation of the family leave the 

 gelatino'us mass and swarm out, to settle down quickly in some other place. 

 It is probable that the formation of a new family is preceded by a longish 

 stage of rest, perhaps there are several resting generations, but we have 

 no observation on this point. In Gl. mucosus the full-grown cells are ggth to 

 s'gth of a millimeter long, the " phytodoms," or family stocks forming at the 

 bottom of little ponds, attain the size of an apple, and are of compressed 

 globular, often lobed shape, till they at length break up, and come to the 

 surface of the water in irregular fragments. The gelatinous mass has a 

 peculiar greenish spotted aspect, which depends upon subordinate groups of 

 generations being more closely packed together. Another form, perhaps 

 specifically distinct (Gl. minor), appears in the springs at Freiburg, in the 

 spring, in the form of light yellowish-green, often pear-shaped " stocks," at 

 most as large as a hazel-nut, attached to the sides of the gutters of the 

 springs, finally becoming detached, swimming, and shapeless. The cells arc 

 somewhat smaller, ifoth to T ' s th of a millim. long. 



