232 THE MICROSCOPE AND ITS REVELATIONS. 



jugation;' in which two cells, apparently similar in all respects, fuse 

 together for the production of a ' zygospore,' which (like the seed of a 

 Flowering-plant) can endure being reduced to a quiescent state for an un- 

 limited time, and may be so completely dried up as to seem like a par- 

 ticle of dust, yet resumes its vegetative activity whenever placed in the 

 conditions favorable to it. The conjugating process commences by the 

 putting-forth of protrusions from the boundaries of two adjacent cells, 

 which meet, fuse together (thereby showing the want of firmness of their 

 ' ectoplasms '), and form a connecting bridge between their cavities (K). 

 The fusion extends before long through a large part of the contiguous 

 sides of the two cells (L); and at last becomes so complete, that the com- 

 bined mass (M) shows no trace of its double origin. It soon forms for 

 itself a firm cellulose envelope, which bursts when the ' zygospore ' is 

 wetted; and the contained cell begins life as a new generation, speedily 

 multiplying, like the former ones, by binary subdivision. It is curious 

 to observe that during this conjugating process a production of oil-parti- 

 cles takes place in the cells; those at first are small and distant, but 

 gradually become larger, and approximate more closely to each other, and 

 at last coalesce so as to form oil-drops of various sizes, the green granular 

 matter disappearing; and the color of the conjugated body changes, 

 with the advance of this process, from green to a light yellowish-brown. 

 When the zygospore begins to vegetate, on the other hand, a converse 

 change occurs; the oil-globules disappear, and green granular matter 

 takes their place. This is precisely what happens in the formation of 

 the seed among the higher Plants; for starchy substances are transformed 

 into oil, which is stored up in the seed for the nutrition of the embryo, 

 and is applied during germination to the purposes which are at other 

 times answered by them. 



230. If this (as seems probable) constitutes the entire life-cycle, of the 

 Palmoglcea, it affords no example of that curious ( motile' stage which is 

 exhibited by most Algal protophytes in some stage of their existence, and 

 which constitutes a large part of the life history of the minute unicellular 

 organism now to be described, the Protococcus pluvialis 1 (Plate vin., fig. 



1 The Author had under his own observation, thirty-five years ago, an extra- 

 ordinary abundance of what he now feels satisfied must have been this Protophy te, 

 in an open rain-water cistern which had been newly cleaned-out. His notice was 

 attracted to it by seeing the surface of the water covered with a green froth, 

 whenever the sun shone upon it On examining a portion of this froth under the 

 Microscope, he found that the water was crowded with green cells in active 

 motion; and although the only bodies at all resembling them of which he could 

 find any description, were the so-called AnimalcMles constituting the genus 

 Chlamydomonas of Prof. Ehrenberg, and very little was known at that time of 

 the ' motile ' conditions of Plants of this description, yet of the Vegetable nature 

 of these bodies he could not entertain the smallest doubt. They appeared in 

 freshly collected rain-water, and could not, therefore, be deriving their support 

 from Organic matter : under the influence of light they were obviously decompos- 

 ing Carbonic acid and liberating Oxygen; and this influence he found to be essen- 

 tial to the continuance of their growth and development, which took place 

 entirely upon the Vegetative plan. Not many days after the Protophy te first 

 appeared in the Water, a few Wheel-animalcules presented themselves: these fed 

 greedily upon it, and increased so rapidly (the weather being very warm) that 

 they speedily became almost as crowded as the cells of the Proctococcus had been; 

 and it was probably due in part to their voracity, that the plant soon became less 

 abundant, and before long disappeared altogether. Had the Author been then aware 

 of its assumption of the ' still ' condition he might have found it at the bottom of 

 the cistern, after it had ceased to present itself at the surface. The account of 

 this Plant given above is derived from that of Dr. Conn, in the " Nova Acta Acad. 



