1552 



ZOOLOGICAL SOCIETY BULLETIN 



While writing this article two hermit crabs 

 were fighting in the aquarium tank where there 

 are a dozen or more specimens. The victor lost 

 his right biting claw in the fray and without 

 showing the least concern drew the body of the 

 victim out of the shell and ate the softer parts. 

 It was impossible to get a picture of the fight 

 owing to the lateness of the hour. 



THE WATER BEAR 

 By Ida M. Mellen 



THE most elusive animal in the world, and, 

 if we omit the horse shoe crab, (Limu- 

 lus) and the headless fish, (Amphioxus), 

 perhaps the most remarkable, is the water bear, 

 Tardigrade. 



The horse shoe crab and the headless fish 

 are not so difficult to obtain and place under ob- 

 servation, but a microscopist may look for a 

 water bear many moons ere his search will be 

 rewarded ; and then, though he give it but a tea- 

 spoonful of water to roam in, he may not find it 

 a second time — so extremely minute is the 

 alluring creature. 



After several years of intermittent micro- 

 scopy, I found a water bear. She favored me 

 with her presence two days and on departing 

 left a souvenir of inestimable value, — her old 

 skin with two eggs inside, and these hatched. 

 She measured not more than 16/1000 of an 

 inch, and her offspring were, of course, consid- 

 erably smaller. 



Tardigrada, meaning slow walker, is not the 

 most appropriate name that could have been be- 

 stowed. It does not convey the impression of 

 perpetual motion which one receives on viewing 

 the animals. The eight tiny feet never rest, 

 their long claws grasping at everything near 

 them as their owner incessantly works his way 

 about. 



Except for twice too many feet and no tail, 

 the Tardigrade slightly suggests the bear in its 

 aspect and is therefore commonly called water 

 bear and bear animalcule. Some of its early 

 describers — a popular notion then prevailing 

 that bears lick their cubs — hazarded the guess 

 that it resembled an unlicked bear cub. As a 

 matter of fact, no one knows whether bears lick 

 their cubs or not, since the she-bear (as I am 

 informed by Mr. Hollister of the Washington 

 Zoo) retires into complete seclusion for six 

 Aveeks when the young are born and would kill 

 them if disturbed, at least during the first few 

 days ; and there is really no known animal to 



THE WATER BEAR 

 From a dravving by Ida M. Mellen. 



which the Tardigrade may be likened with cer- 

 tainty. 



In the matter of classification, it has been 

 called an animalcule, a crustacean, a worm, and 

 a spider. While it lives amicably with proto- 

 zoa, flat worms, rotifers and snails, it is zoo- 

 logically evasive and something of an aristo- 

 crat, refusing to be closely associated with anj' 

 other animal, yielding to no real grouping at 

 all, but occupying a separate heading all by 

 itself — at present near the spiders — under the 

 large order of jointed- footed animals. This is 

 rather awkward, because there are no joints 

 whatever in its feet, and latest rumor is that it 

 will next find itself back among the worms, 

 from which group of animals it is now thought 

 to be an offshoot. 



The Tardigrada are remarkable creatures ; 

 not only remarkable to look upon, but wonder- 

 fully put together. They are male and female. 

 Besides head, feet and claws, they possess a 

 mouth, pharynx, oesophagus, teeth, stomach, 

 muscles, and sometimes eyes — but never any 

 tail. The body is composed of beautiful, regu- 

 lar cells that delight the physiologist, especi- 

 ally the student of histology, the science of the 

 tissues ; yet the Tardigrade possesses no con- 

 nective tissue. It has a brain, a nerve cord, a 

 chain of ganglia, and optic nerves, and an or- 

 ganism that exhibits no signs of degeneration; 

 yet the animal boasts neither lungs, gills, kid- 

 neys, heart, nor blood vessels. 



Certain bacteria and other vegetable organ- 

 isms have been observed flourishing in its body 

 fluid, but work no apparent injury to their busy 

 host. Outwardly it appears defenseless. Its 

 teeth are used only on the plants it eats, and its 

 claws are never set in the hide ol friend or foe, 

 so far as we can ascertain, but serve only to 

 grasp surrounding objects to help the tiny crea- 

 ture over his watery ground ; but the salivary 

 glands are said to secrete poison. 



Europeans first recorded the Tardigrades and 

 described species that live in salt water as well 

 as fresh. The fresh-water species has generally 



