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HARDWICKE'S SCIENCE-GOSSIP. 



A PAGE OF THE LIFE-HISTORY OF 



STEPHANOCERAS EICHORNH. 



By W. H. Harris. 



DURING the summer of 1887, I was fortunate 

 enough to become possessed of some specimens 

 of Stcphanoceras Eichornii. Often had I searched for 

 this king of animalcules in the numerous pools and 

 dykes of this neighbourhood, and which had from 

 time to time furnished specimens of rare forms ; 

 but never had I been able to take this creature. Now, 

 however, I had a large colony close at hand. A 

 tank which had stood in the slanting rays of light 

 coming through a window having a south-easterly 

 aspect was changed to another window facing the 

 north-east ; it had stood in the former position for two 

 or three years ; the results not being satisfactory, the 

 change of quarters was decided upon and carried 

 into effect in the early spring. In the following July 

 a few specimens appeared, became more numerous 

 during the ensuing three months, and continued in 

 gradually diminishing numbers until the close of the 

 year. 



I had these creatures under observation for two 

 months, and I propose to place upon record some of 

 the phenomena which came under my notice, as an 

 instalment towards the entire life-history of this 

 exceedingly beautiful and interesting creature. 



A word as to the method adopted for continuing 

 the observations may be useful to others similarly 

 employed. Simple means are frequently the best. The 

 outfit consisted of a few thin flattish watch-glasses 

 and a square of thin cover-glass. The specimen to 

 be observed was removed into a watch-glass, with a 

 small portion of the plant to which it was attached ; 

 a sufficient quantity of water given to cover the 

 specimen. The cover-glass was then floated on the 

 surface and observations made. When these were 

 completed, the cover-glass was removed, a liberal 

 supply of water given, and then placed aside under a 

 wine-glass to exclude dust, and retard, as far as 

 possible, the rapid evaporation caused by summer 

 temperature. 



Experience taught me that the secret of successfully 

 preserving the specimens in good health, lay in 

 removing the cover-glass ; if this were not done, 

 symptoms of declining health soon manifested them- 

 selves, the verticillate setse lost their energy and 

 contour ; some dark spots collected in the main trunks 

 of the arms ; the whole organism languished, and if 

 not relieved, death soon ensued. Specimens far 

 advanced towards dissolution recovered under the 

 changed conditions and fulfilled the object of their 

 existence. Air, and plenty of it, was the key to success. 



Until this conclusion was reached, my observations 

 were liable to be interrupted at a very interesting 

 point, and the labour expended lost to some extent. 

 Soon,however, certain questions suggested themselves, 



answers to which could alone be given by the organ- 

 isms. It was with the view of extracting these answers 

 something like systematic obsevations were continued 

 over the greater portion of the time mentioned. 



How are the young produced ? I had noticed that 

 adult specimens when taken from the tank contained 

 ova in different stages of development ; that these 

 decreased in number, but could not be found in the 

 tube, as is the case with many other tube-dwelling 

 rotifera ; that after a short time a young specimen 

 would be found in all respects, save one, like its 

 parent, the difference consisted of size alone. Soon it 

 was found they were ovoviviparous, the ovum being 

 excluded and remaining in contact with the parent ; 

 the young one shortly after made its escape, and for 

 a short time led a free life, roaming gracefully through 

 the water until it settled down to the stern realities 

 of its existence. 



I was never fortunate enough to witness the actual 

 exclusion of the ovum, although many hours were 

 specially devoted to this end ; that the act is a rapid 

 one there is not the slightest doubt, as on several 

 occasions the withdrawal of the eye for occasional 

 relief was sufficient to thwart the object in view. 



When the young first escape from the ova they are 



Fig. 29. — Young Stephan- 

 oceros just emerged. 



Fig. 30. — First formation of 

 Tube. 



mere sac-like creatures with a fringe of cilia around 

 the anterior end, the posterior end contracts rapidly, 

 terminating in a rounded point. The following ex- 

 ample may be taken as fairly illustrative of the early 

 stages of the organism and the time occupied, but as 

 the season advanced and temperature fell the changes 

 took longer time to effect. 



August 29th, an ovum was excluded at 9.30 A.M., 

 remaining attached to the lower part of the body of 

 the parent, the young one emerged at 10.30, swam 

 freely until II A.M. ; it then settled down, and in 

 a few seconds attached itself permanently ; then 

 elongated and contracted itself to its utmost extent, 

 gave a few convulsive turns, and in three minutes 

 from the time of settling the first portion of its future 

 dwelling-place was distinctly visible. The idea con- 

 veyed to the mind by the series of movements I have 

 attempted to describe was that it had thus divested 

 itself of a very thin and hyaline pellicle, but whether 

 this was really the fact remained undecided : the 

 main bulk of the adult tube is considered to be a 

 secretion, but this would not necessarily clash with 

 the above idea ; on the contrary, it can be readily 

 conceived it would materially assist the flow of the 

 fluids in a proper direction for the purpose it has to 



