JrLY 1, 1898.] 



KNOWLEDGE. 



117 



cases and antennas, the oral parts and the respiratory 

 limbs, the bright spines and feathered hairs — all the 

 delicate structure, glassily transparent, is exposed to view, 

 like the wreathed pearls, the unclasped jewels, and the 

 rich attire which Madeline had put off on that famed Eve 

 of St. Agnes, when, enamoured and entranced, " Porphyro 

 gazed upon her empty dress. " 



The I'hyllopod's story, however, is not exclusively 

 romantic. The cultivation of many species in a small bowl 

 is convenient for the observer, but it also gives the stronger 

 forms great and not always unwelcome facility for preying 

 on the weaker. A couple of the Kstherin ijihoni, figured 

 in the first chapter, caused me much surprise one summer 

 for two reasons. First, the pair attained an unwonted 

 size, which implied that the conditions were healthy ; but, 

 secondly, contrary to custom, all other animals, even those 

 of the same species, though grown under the 

 same conditions, speedily disappeared. At .,-, 



last the pair that had waxen fat were put 

 to death, just to see what would happen, and 

 straightway a brood of youug Estheria grew 

 up and prospered. It seems scarcely uncharit- 

 able to infer that the long-dominant pair had 

 thriven on cannibalism. In the kindred genus, 

 Limnndia, there is another strange circum- 

 stance which interferes with romance. Of 

 this genus only two species are as yet known 

 — one European and one American — and in 

 neither of them has any specimen of the male 

 sex been observed. The propagation, according 

 to Prof. G. 0. Sars (an unsurpassed authority), 

 is exclusively parthenogenetic. " Males," he 

 gays, " in spite of the most careful investiga- 

 tion, have not yet been found, and probably 

 do not exist." It is not a little wonderful that 

 these Amazons should occur in a group which 

 commonly has both sexes abundantly repre- 

 sented. But perhaps the effacement of the 

 inferior sex will prove even here not to be 

 quite so absolute as for the moment it seems, 

 although the Russian and Hungarian natu- 

 ralists, Krynicki and Chyzer, who claim to have 

 observed the males, may have been deceived 

 as to the species they examined. 



The division of the Phyllopods with a cara- 

 pace or dorsal shield contains the largest of aU 

 the species, Apus aitstrnlitnsis Spencer and Hall, 

 nearly three inches long, and Ltjii'luriis inacni- 

 nis, exceeding an inch and a half in length. Fig 

 It is in this division also that the legs reach the Fig 

 surprising number of a hundred and twenty- 

 six. This being the case, it will appear an odd thing that 

 the primary genus, which is scarcely or not at all to be 

 distinguished from Lejiidunis, should have been called Apu^ 

 — that is to say, " the legless." The explanation is this. 

 The ingenious Dr. Johannes Leonhard Frisch, who in 1732 

 published the first description and figures of what he called 

 " the fin-footed lake worm with the shield," did not over- 

 look the little packet of almost innumerable leaflets under 

 the trunk, but decided that they were more like fins than 

 feet. He therefore obligingly left it open for those who 

 thought them legs to call this " insect " or " water worm " 

 a, polypus — that is, " many legs," while for him it was pre- 

 ferentially an aptia, or " no legs." 



In the Apodidte it may be noted that the males are very 

 rare ; and abundant as the females are in some parts of 

 the world, the student in England may not always find 

 specimens at his command. He can always solace himself 

 by having recourse to the Cladocera. These are distin- 



guished by the conspicuously branched second pair of 

 antenna', which are their swimming organs. They content 

 themselves with a comparatively parsimonious number of 

 legs— from four to six pairs— and have the whole body 

 except the head encased in valves, which, for the benefit of 

 the naturalist, are often conveniently transparent. In all 

 countries may be found some puddle, pool, or pond, some 

 swamp, or tarn, or lake ; and therefore in all countries the 

 zoologist may recognize a link with home by finding 

 Daphnia puh'x or one of its near relations. In numbers 

 numberless may members of this prolific tribe be obtained 

 by dipping a net into almost any horsepond. Their 

 movements can be studied by transferring a few to a 

 tumbler of water ; their organization by isolating one in a 

 watch-glass under the microscope. No Runtgen rays are 

 needed. The living works of the machine are plain for 



on left, Daphnia carinata, var. intermedia Sare, female with epMppium. 

 on right, typical form of Daphnia carinata King, ovigerous female.* 



all folk to see. It is worth taking a little trouble to 

 observe the winking of that ever-trembling eye, the motions 

 and adornment of the branchial feet, the little pulsating 

 heart, the strokes of the spiniferous tail, the curious 

 sinuosity of the intestine. One may chance to see the 

 eggs pouring from the ovary and taking shape in the 

 maternal pouch. Often within that pouch may be seen 

 numerous eggs or young ones forward in development. 

 Daphnia islike^piw, the prevalent method of reproduction 

 being, as Dr. G. S. Brady expounds the matter, '• not 

 sexual at all, but parthenogenetic, the female producing 

 and detaching in rapid succession broods of young, which 

 are the restilt of the development, not of fertilized eggs, 

 but of mere buds or " pseudova." The fertilized eggs, 

 the winter eggs, the eggs which keep and pass the winter 



* ■' On Fresh-water Entomostraca from the Neighbourhood of 

 Sydney, partly raised from Dried Mud." By G. O. Sars. PI. I. 1896. 



