600 SCIENTIFIC RECORP FOR 1884. 



seen, as it works its way forward or drags itself backward by means of 

 its i^odal hooks and 6«pines. Later on, tJie anterior extremity thickens 

 and becomes more and more opaqne, and, as Dr. Leidy has observed, 

 'feebly annulated,' presumably from the adherence of effete particles, 

 and their compression by the repeated withdrawal of th(! ciliated tenta- 

 cles into the mouth of the tube. This method of prolongation must con- 

 tinue during the residence of the worm, and in consequence, if supported, 

 it may sometimes reach a length which is several times that of its inhab- 

 itant." {Proc. Acad. Nat. Sc. Phila., 1884, pp. 48, 49, 21, 22.) 



Earth-worms in New Zealand. — The extensive modifications which the 

 boring and concomitant habits of earth-worms effect upon the land, 

 have become familiar through the work of Darwin on those humble 

 animals. The surprising- results effected by worms ou ordinary English 

 land might be made, according to the estimate of Darwin, by an army 

 consisting of an average of about 26,886 to the acre. Later, Henson, 

 from observations conducted in Germany, estimated that in favorable lo- 

 calities about twice as many as were calculated for by Darwin (53,767) 

 existed in garden grounds, while in green fields the number would closely 

 approximate that presented by the great English naturalist. The abun- 

 dance of a New Zealand species has recently been brought to light, and 

 Mr. A. T. Urquhart gives, as the result of his investigations, to an acre 

 of i)asture land near Auckland, the large number of 348,480 worms as 

 found therein ; and on his results being challenged, even this number 

 was greatly increased by subsequent experience. A piece was "laid 

 out into squares of 120 feet, and a square foot of soil was taken out at 

 each corner ; worms hanging to the side walls of the holes were not 

 counted, and in one hole, where the return of worms was a blank, the 

 walls were crowded with worms." As the result, there was an average 

 of 18 worms per square foot, or 784,080 worms per acre. Although this 

 average is in niunber so striking, when compared with those of Darwin 

 and Henson, the difference between the actual weight of the worms is 

 very much less in proportion. "According to Henson, his average of 

 53,767 worms would weigh 356 pounds, while Mr. Urquhart finds that 

 the average weight of the number found by him came to 612 pounds 9 

 ounces," or less than twice the aggregate of the German percentage. 

 The value of the observations on the New Zealand worms would have 

 been much enhanced had their relationship been determined. {Trans. 

 Neic Zealand Imt, v. 26 ; Nature, V. 31, p. 23.) 



Myzostomids. 



The species of Myzostomids. — More than forty years ago Prof. F. S. 

 Leuckart discovered certain singular organisms parasitic on the- arms 

 of the crinoid known as Antedon rosacea, which were recognized as two 

 species of a previously unknown type, and which received from him the 

 generic name Myzostoma; one of the species was called M. glabrmn and 



