ON MICROSCOPIC DISCOVERY. 



627 



triehelis. Flask-shaped. 12. Monas erultesce ns. L>. 

 Monus Iiya>ina.U. Monas kolpoda.\5. Monas Ovalis. 

 Ib. Monas polytoma. 17. Monas umbra. 18. Monas 

 volvox. Revolving monad. 



II. PROTEUS. An invisible, very simple 

 pellucid worm, of a variable form. 



" We now arrive at a larger class of ani- 

 malcules, whose habits are highly interesting 

 and curious : indeed there are few in the ex- 

 amination of which I have been more de- 

 lighted. This gratification arises not so much 

 from any complexity in their organization, 

 which in comparison with the Brachionus, 

 and some of the Vorticella, is more simple, 

 but from the great power they possess of di- 

 lating their bodies ; and their motions being 

 slow, the observer is enabled to examine their 

 changes of form distinctly." 



Fig. 66. The melting Proteus. " The 

 drawing of this animalcule was taken from 

 a specimen found in some water containing 

 duck-weed (lemna major), in the month of 

 March. Miiller states he only saw them 

 twice. Their diameters vary from l-600th to 

 l-300th of an inch." 



PROTEUS SPECIES. 



1. Proteus diffluens. Branching itself out in a variety 

 of directions. 2. Proteus Tenax. A globular mass, ex- 

 (ending a process terminating in a fine point. 



III. VOLVOX. An invisible, very simple, 

 pellucid, spherical worm. 



" The animalcules belonging to this genus 

 are of a globular form, and revolve in the 

 water. Some of the species are so large as 

 to be discerned by unassisted vision, while 

 others are very diminutive. Ehrenberg lias 

 not demonstrated their digestive organization ; 

 but in a note to his table, conceives they ought 

 to follow the monads. In this genus is in- 

 cluded that beautiful animalcule, called the 

 volvox glubator, which forms so interesting a 

 spectacle in the solar and gas microscopes." 



Fig. 67. The vegetable Volvox. " Thi 

 animalcule is rather scarce. Its most inter- 

 esting character is the short time which it 

 requires in arriving at maturity, and under- 

 going all its changes. In the space of hall 

 an hour, when fed with an infusion of indigo 

 a single globule may be observed to emerge 

 from a naked branch, increase in size, anc 

 divide into a cluster of smaller ones ; these 

 increase also, and after revolving, and bring- 

 ing a current of food towards them, finally 

 separate, and swim away, each of the young 

 ones commencing a similar course. It con> 

 sists of several opaque branches : at the ter 

 initiation of eacli is a small congeries of egg 

 shaped transparent bodies. Miiller, whc 

 seems only to have seen them once, mistool 

 them for a vegetable production, until h 



bserved the -clusters to separate from the 

 ranch, and swim about at pleasure." 



" These animalcules produce a rapid cur- 

 ent of water towards them, as indicated by 

 he arrow in the figure ; and if supplied with 

 lenty of coloured food, as indigo, they will 

 lot only assume the colour of the particles, 

 jut may be seen to increase in size, under 

 he eye of the observer. When the cluster 

 s fully developed, it breaks, off, and swims 

 away, revolving as it proceeds. After roving 

 about for a few minutes in search of a proper 

 lidus to attach itself to, it spins a very delicate 

 hread, like a spider's web, one end of which 

 t fixes to the substance it has selected ; this 

 ilamentjwhen drawn out to the proper length, 

 ncreases in size, and assumes the deep blue 

 colour of the indigo, while the end of the 

 stalk which it left shoots forth a new cluster. 

 The current above mentioned is sometimes 

 Droduced without any revolution of the cluster 

 of globules ; at other times I have observed 

 he whole cluster to revolve. The magnify- 

 ing power which I employed, while making 

 the drawing of this figure, was nearly 500 

 times. The medium diameter of the clusters, 

 while attached to their branches, I find to be 

 about the 800th part of an inch ; and when 

 fully developed and separate, about 1- 400th 

 of an inch. Miiller discovered these animal- 

 cules in river water in the month of Nov- 

 ember. Those on which the above observa- 

 tions were made I found in the month of 

 June, in some pond-water." 



Plate 27, fig. 35. Volvox globator Spheri- 

 cal membranaceous volvox. 



This is a transparent globule, of a greenish 

 colour ; the foetus is composed of smaller 

 greenish globules. It becomes whiter and 

 brighter with age, moves slowly round its 

 axis, and may be perceived by the naked eye. 

 But to the microscope the superficies of this 

 pellucid membrane appears covered with 

 molecules, as if it were granulated, which has 

 occasioned some observers to imagine it to be 

 hairy ; the round pellucid molecules that are 

 fixed in the centre are generally larger in 

 those that are young. The exterior molecules 

 may be wiped oft', leaving the membrane 

 naked ; when the young ones are of a proper 

 size, the membrane opens, and they pass 

 through the fissure ; after this the parent is 

 dissipated. They sometimes change their 

 spherical figure, the superficies being flattened 

 in different places. Most authors speak of 

 finding eight lesser globules within the larger ; 

 but Miiller says, that he has counted thirty 

 or forty of different sizes. This wonderful 

 capsulate situation of its progeny is well 

 known ; indeed, it often exhibits a second and 

 third generation within it. Leeuwenhoeck 

 was the first who noticed this curious animal- 



