NOTES ON PLYMOUTH HYDROIDS. 149 



fascicled stems of hydroids may have arisen. In some of the speci- 

 mens the aggregation of root-stalks would doubtless be sufficiently 

 rigid to support themselves in an erect position after the stem to which 

 they cling had died, and we should then have a loosely put together, 

 fascicled stem, which a little further differentiation would convert into 

 a typical polysiphonic hydrocaulus. 



The tubular extension of the hydrothec* reminds one of similar 

 structures in the genus Cryptolaria, which contains several species 

 further related to the one under discussion, in having the operculum 

 composed of convergent segments. 



CusPiDELLA GRANDis, Hincks. In looking over my Plymouth series 

 of hydroids after returning to America, I found specimens of this 

 species growing over the stems of Halecium tenellum. A careful 

 examination of the stems of the larger hydroids is frequently repaid 

 by the discovery of one or more species of minute parasitic forms 

 which escape the casual observer, and it is quite likely that a number 

 of new species would reward the patience of any one who would devote 

 himself for a time to a search for these forms on British coasts. 



Halecium tenellum, Hincks. A number of colonies with female 

 gonangia were taken from a depth of 18 fathoms on April 19th. 

 These specimens closely resemble in several points miniature colonies 

 of H. lahrosum, Alder, especially in the shape of the gonangia and the 

 wrinkled appearance of the stems, which, however, are monosiphonic. 

 Indeed, one cannot wonder that Alder mistook H. tenellum for the 

 young of H. labrosum. Out of a large number of colonies of 

 H. tenellum from Plymouth, there are none over half an inch in 

 height, and they very generally show the reduplication of the margins 

 of the hydrophores, which Hincks mentions as a characteristic feature. 



Plumularia pinnata, Linn. This is by far the most abundant 

 Plumularian at Plymouth, and afforded an excellent opportunity to 

 study the morphology and reproduction of the group. 



The Ncmatoijhores. There is a great deal of confusion of terms 

 regarding these structures. The name properly applies to both the 

 sarcodal process and the chitinous receptacle into which it retracts, 

 although it is often used to denote either one of these structures. The 

 terms " sarcostyle," denoting the sarcodal process, and " sarcotheca," 

 denoting the chitinous receptacle, have now come into general use. 

 Hincks' description of F. pinnata is incomplete, in that it does not 

 notice the sarcostyles which occur without the investing sarcothecie. 

 One pair of these naked sarcostyles is found in the usual position of 

 the supracalycine nematophores, and another pair is in the axil of each 

 hydrocladium. 



The structure of the nematophore.'^ has been the subject of much 



