762 



SCIENCE. 



[Vol. II., No. 45. 



(cndocarp) is found thick, horny, and in all 

 respects like that of J. nigra. Tlie lower por- 

 tion of the shell projects into the lower sec- 

 tion of the nnt, and resembles the point of a 

 butternut. The engraving is from a carefuUj' 

 executed drawing, representing the nut of nat- 

 ural size. 



The matter as above presented is left in the 

 hands of those more familiar with subjects in 

 teratology. There is no doubt that in the 

 cross-fertilization of plants we ma^- have a 

 deviation from the jjarent form, even in the 

 development of the seed thus fertilized, or 

 in its surrounding parts. Some strawberr_y- 

 growers are very careful what ' perfect ' varie- 

 ties are grown among their pistillate sorts to 

 fertilize them. The fleshj- receptacle, which 

 is the edible portion of the strawberry, is more 

 remote from the ovules which are fertilized on 

 its surface than the covering of a shellbark or 

 walnut is from the embryo within. 



Hybridization between closely related gen- 

 era is well established in several cases. Sachs 

 mentions that it has been observed between 

 species of Lj-chnis and Silene, Rhododendron 

 and Azalea, Rhododendron and Rhodora, 

 Azalea and Rhodora, Rhododeudrou and Kal- 

 mia, Aegilops and Triticum, and between 

 Echinocactus, Cereus, and Phylocactus. The 

 two genera Juglans and Carya compose a small 

 order of closely related species. A study of 

 the generic characters, as set down in tli£ 

 classification of these species, does not reveal 

 anj' more striking 'difference than that shown 

 in the exocarp. The male and female flowers 

 are separated on the same tree (monoecious), 

 and pollen must pass from flower to flower. 

 This fertilizing-dust is produced in great abun- 

 dance ; and the distance between the black 

 walnut and the pecan, or even the shellbark, 

 is easily traversed by the pollen. There is 

 probablj' no difficulty in the way of hybridiz- 

 ing from a difference of time in the flowering 

 of the species. Bvkox 1). IIalsted. 



New York, Oct. 26, 1883. 



MAN A YUNKIA SPEC [OS A . 

 lisr a paper, ilhistrated with a plate, recently pre- 

 sented to the Academy of natural sciences of Philadel- 

 phia, Professor Joseph Leidy describes Manayunkia 

 as 11 cephalobranchiate annelid living in fresh water, 

 the only one of the order yet discovered not living in 

 the ocean. It was found with the equally remarkable 

 polyzoan Urnatella, with its lubrs of mud attached 

 to the same stones, in the Scluiylkill River, at Phila- 

 delphia. It was first noticed, and a brief descrip- 

 tion given of it, in the Proceedings of the academy 

 in 18J8. 



Manayunkia is nearly related to the marine genus 

 Fabricia, with a species of which, described by Pro- 

 fessor Verrill, the writer compared it, through S|fleci- 

 menscollected atNewport, l'i.I.,and Gloucester, Mass. 

 Manayunkia has not been observed elsewhere until 

 recently, when it was found by Mr. Edward Potts, 

 attached to a fragment of piue bark from Egg-Harbor 

 River, New Jersey. 



The tubes of JIanayunkia are simple or compound, 

 and in one instance five tubes branched and were 

 j)endent from a common stock in a candelabra-iike 

 manner. The little worm is very active and sen- 

 sitive, and on the slightest disturbance withdraws 

 into its tube. When quiet it protrudes its head, and 

 spreads its cephalic tentacles or branchiae. The ma- 

 ture worm is three or four niillinielres long, and is di- 

 vided into twelve segments, including the head. The 

 color is olive-greenish, due to the bright green blood 

 circulating in the vessels of the animal. The head 

 Is furnished with a pair of conspicuous eyes, and 

 supports a lateral pair of lophophores, each provided 

 with si.xteen cylindrical tentacles, invested with ac- 

 tively moving cilia, and closely resembling those of the 

 polyzoa. The segments succeeding the head are pro- 

 vided witli lateral fascicles of locomotive setae, and 

 in addition, except the first one, are further provided 

 with fascicles of pedal hooks. 



The seventli segment is much largei- than any of 

 tlie others, and further differs from them in being 

 greatly expanded in front; so that it gave rise to 

 the idea that the worm undergoes division, though the 

 process was at no time observed. The intestine is 

 quite simple. The chief portions of the vascular 

 system consist in a vast sinus enclosing the intesti- 

 nal canal, giving otf lateral jjairs of branches to the 

 segments, and a large vessel which extends from each 

 side of the head into one of the tentacles, which is 

 larger than the others. The blood is bright green, 

 and is observed to be incessantly pumped into and 

 expelled from the larger pair of tentacles. Ovaries 

 occupy tlie segments from the fourth to the sixth in- 

 clusive. Organs supposed to be the testes extend 

 from within the head into the third segment. 



Manayunkia lays its eggs and rears its young within 

 its own tube. The young, measuring about three- 

 fourths of a millimetre, had the body divided into 

 nine segments, and each lophophore provided with 

 four tentacles. 



In the species of Fabricia of our coast tlie number 

 of segments of the body is the same as in Manayun- 

 kia; but the lophophores supporting the tentacles, 

 instead of being simple, are trilobed or trifurcate. 

 Fabricia has eyes in tlie tail, or last segment, as well 

 as in the head, which is not the case with Mana- 

 yunkia. 



DRAINAGE SYSTEM AND LOESS DFS- 

 rillDUTION OF EASTERN rOWA. 



These are described by Mr. W. J. McGee in a 

 recent communication to the Philosophical society of 

 Washington. The Mississippi River, where it forms 

 the eastern limit of Iowa, flows somewhat to the east 



