286 ROBERT TRACY JACKSON ON THE 



an area of quiet water within the pipe, in which the fiy could settle and attach them- 

 selves to the smooth glass; (3) the alisolute shutting-out of violent currents which would 

 detach them from their precarious abiding places. 



I first found spat on the glass on the 25th of July, 1887, and on the 28th took oiit a 

 pane 6 by 4^ inches square on which I have connted eighty-two young oysters, as it is 

 still in my possession intact. This was only excei^tional in the size of the glass, as other 

 pieces bore nearly or quite ns many spat proportionally to their area. Spat were secured 

 in the ]3ipes until the 29th of October, 1887, when few were left, large numl)ers having 

 dropjjed off by the natural dissohing action of the sea-water upon the organic cement 

 by which they are attached. In 1888 the first oysters wei-e found on glass on August 

 1st, and they continued to set into the month of Septembei-. The hiteness was probably 

 due to the comparative coldness of the summer. 



Besides oysters, the young of many invertebrates and algjB attached themselves to 

 the glass, affording admirable opportunities for studying them alive and undisturbed. 

 The following attached invertebrates were noted: 3Iolc/nla 7nanhrdtensis, YerriU ; Bcdanus 

 halcmoides, Stimj^son; Serpulas, and other tubicolous worms; Crepidulafornicata^ Lam.; 

 C. plana. Say; Ostrea virylniana, Listei'., in profusion; Aiiomia ylahra, Verrill, nearly 

 as abundant as the oysters; Pecten irradians, Lam., attached by a byssus, both very 

 young and quite large individuals, varying from 4 to 13 mm. in height; Modlola plica- 

 tula. Lam., attached by a byssus; Argina pexata, Gi'ay, attached by a byssus; Mem- 

 hranipora j)ilosa, Farre, often in large sheets; Escharella variabilis, Verrill.^ 



The drain-pipes formed a sort of trap, into which many fi'ce-moving, crawling, or swim- 

 ming molluscs found their way. When in the pipe they would have some difficulty in 

 getting out, and much valuable material was thus obtained. The following Gasteropods 

 Avere found entrapped: Scalaria lineata. Say; Urosalpinx cinerea, Stimpson. This gas- 

 teropod destroys many oysters both young and adults by boring into the shell and 

 killing the animal. I have not seen holes bored by Urosalpinx in Anomias, though they 

 are quite as exposed as are oystei's to its attacks. Littorhia litorea, Menke, was found 

 enti'apped, both adults and young, in great abundance. In moving about on the more or 

 less dirt-covei-ed glass, this animal makes a trail by the lingual ribbon with which it as- 

 siduously scrapes the glass for its food. The tracks consist of zigzag series of short, 

 parallel lines of cleaned glass, arranged with the longer axes in the direction of the trail. 

 The short lines are almost confluent with the lines of the next succeeding row; I)eing 

 at first nearly confluent on one side and then on the other, producing a zigzag ])attern as 

 the animal moves along. Ilyanassa obsoleta, Stimpson, was found in great abundance 

 in the pipes. This species makes a track similar to that of Littorina, but much smaller, 

 as might be supposed from the size of the animal. The differences are that the individ- 

 ual, ])arallel, short lines are less distinctly separable one from another and there is a 

 much largei- angle between the successive zigzag series of lines in the ti-ack of Ilya- 

 nassa, than is the case with the track of Littorina. The last two gasteropods did good 



' Our sea-anemone, MelrUUnm man/iiintum, at.taclies it- proba1)ly successful metliofl to adopt in studying tlie de- 



self freely to glass slides ^vllen iu confinement. The plan veloi)nient of corals -vvliere very tine results might be ob- 



of placing glass iu enclosetl traps would be a desiratjle and taiucd l)y its employment. 



