390 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



the Hydroids that occur on the piles of wharves, and on the under side 

 of floating timber, is the Parypha erocea, (Plate XXXVI, fig. 274.) 

 This species grows in great luxuriance upon the piles, especially in 

 those harbors where the water is somewhat brackish. It forms large 

 clusters of branching stems, often six inches or more in height, each of 

 which is surmounted by a beautiful, flower-like, drooping head of a pink 

 or bright red color. These heads are often broken off, or even volun- 

 tarily cast off, when the animals are unhealthy, but new ones are soon 

 reproduced, and, therefore, this does not seem to be a very serious acci- 

 dent, though certainly a very inconvenient one, for the mouth, stomach, 

 tentacles, and most other organs are all lost when these "heads" 

 drop off. This species does -not produce free-swimming medusas, but 

 the buds, corresponding to those that develop into free medusas in many 

 other cases, in this remain attached to the heads in drooping clusters, 

 looking like loose clusters of light red grapes, in miniature. 



The buds produced by the hydroid-heads of one colony are either all 

 males or females, and, while attached to the hydroid-heads, eggs or 

 spermules are developed within them ; the eggs are fertilized and de- 

 velop into young hydroids, which, when finally expelled, are provided 

 with a circle of slender tentacles, and need only to attach themselves 

 to some solid substance by the basal end of the body to become fixed, 

 tubularian hydroids, similar to the old ones in many respects, though 

 still very small and simple in structure. These young tubularians swim 

 and crawl about for a time, and after attaching themselves they rap- 

 idly grow larger and produce stolons from the base, from which buds 

 arise that develop into forms like the first one ; other buds are pro- 

 duced from the sides of the sterns^ which also become like the others, 

 and in this way the large clusters of tubularians are rapidly formed. 



Several species of Campanularians are also to be found attached to 

 the piles and timbers of wharves and bridges. At Wood's Hole the 

 most abundant species was Obelia pyriformis, which grew in great pro- 

 fusion on the piles just below low- water mark. It is a delicate and much 

 branched species, with elongated, pear-shaped, reproductive capsules, 

 and is beautifully phosphorescent. On the hull of an old wreck in 

 Wood's Hole passage, where the tide flows with great force, the Obelia 

 flabellata was found in abundance, though it does not appear to have 

 been noticed on this side of the Atlantic before. It has very elongated, 

 slender, simple, but crooked stems, with numerous, alternate, short, 

 forking, fan-shaped branches 5 these generally fork close to their origin 

 the divisions diverging in opposite directions. The hydroid calicles 

 (hydrothecas) are small, cup-shaped, or broad bell-shaped, with a smooth 

 rim, and they are borne on slender pedicles that are of various lengths? 

 but mostly short and composed of only four to six rings. The repro- 

 ductive capsules (gonothecas) are urn-shaped, with a short, narrow neck; 

 they are borne ou short pedicles, of few rings,' arising from the axils of 

 the branches. Some of the specimens were eight or ten inches long. 



