20 AMERICAN HVDROIDS. 



nopals the margins of the nematophores are finely creiuilated. In most other forms the margins 

 are even. 



Ill Nudithcca ilalli (Plate XXXIV, fig. G) there is no protective branchlet, and in this case there 

 are two bitJtalaniic nematophores attached directly to the gonangia, as so commonly found in the 

 Eleutheroplea. This arrangement is, I believe, unique among the Statoplea. In tliose species of 

 Halicornuria the gonosome of which 1 have examined there are no gonosomal iiernatophores. 



Sarvoxtyh'K. As before intimated, the writer prefers to designate the sarcodal contents of the 

 nematophores as sarcostyles, a name originally proposed by Hiucks and synonymous with the, 

 "extensile process" of Hincks's earlier work; "protoplasmic process," "sarcodal process" of 

 Allmau; " wehrpolypen," " machopolyps," "wchrthier" of von Leudenfeld, Kirchenpauer, and 

 others; "nematophores" of Merejkowsky, Hamaiui, and Weisinann. The last three authors, 

 however, seem to include both the sarcostylc and nematophore, as the terms are here used, under 

 the common and original designation " nematophore." 



It is doubtful if any structure found in the Hydroida has given rise to more discussion and 

 incited to more careful investigation than this. From the time when Allinan, in 1SG4, published 

 his communication On the Occurrence of Ainu-biform Protoplasm and the Emission of 

 Pseudopodia among the Hydroida down to the most recent investigations no structure found 

 in the plumularians has been so carefully and repeatedly studied. Perhaps the growth of our 

 knowledge concerning the sarcostyles can best be understood by means of a brief summary of the 

 principal discoveries, discussed in chronological order. 



In 1SG.S Semper, in his Preliminary Narrative of the Philippines, speaks of a hydroid 

 almost as high as a man, in which the three nematophores associated with each hydrotheca 

 contains "nessel polyps." In his figure 1 of the latter, which are undoubtedly sarcostyles, we 

 have the first representation of these structures that 1 have been able to find, and this figure 

 represents the sareostyle as being a true person with well differentiated endodcrm and a In rye 

 body rarity, thus coming considerably nearer the truth than most writers for the succeeding 

 twenty years. The species in question seems to have been Lytocarpus phiUppinus(K.ii-cheni>aiier). 



In 1SG4 Allmau published the above-mentioned paper,- in which he described the contents of 

 the nematophore as a soft granular mass which could send forth very extensible processes which 

 could be very greatly produced and then so completely retracted as to apparently disappear. 

 These processes have, moreover, the power of sending forth pseud opodia, as does the Amu-ba, 

 and acting in many respects exactly as do certain llhizopods. The author considers that the 

 sarcostyles aie composed of undifferentiated protoplasm in which iiematocysts are sometimes 

 immersed. 



In 18G8 Hincks 3 quotes from the above mentioned paper of Allmau and adds: " I have made 

 similar observations on Plumularia xctacea and P. frulcsci-iis. On a young specimen of the latter 

 species obtained at Oban the uematophores were in a state of great activity, sending out long 

 filamentary processes, which tended some upwards and some down wards, following the course of the 

 stem and branches, and completely investing the zoophyte with a multitude of gossainerlike 

 threads." This author does not regard the nematophores as weapons of ottense, for the reasons 

 that iiematocysts are not always present and that they are not carried out with the pseudopodial 

 processes. He suggests that they may have some connection with the nutrition of the colony. 

 As to the histological structure of the sarcostyles, he regards these organs as '* ectodermal off- 

 shoots somewhat less consolidated than the layer from which they originate." The ectoderm he 

 describes as "of the simplest homogeneous texture, a structureless contractile substance not 

 unlike 'sarcode' in any essential particular.'' 



In 1871 Allrnan 4 reaffirms the structureless composition of the contents of the nematophores 

 and says : " It differs in no respect from the sarcode matter composing the bodies of the Khizopoda, 

 and, like it, it is capable of emitting true pseudopodia." lie says that the iiematocysts are 

 stationary, never being carried out by the sarcode or its processes. 



1 Zeitschrift fiir wissenachaftlicho Zoologie, XIII, pi. xxvni, fig. 4. 



2 On the Occurrence, of Amu>l>itbrin Protoplasm ;mcl the' Kinissiou of Pseudopodia among the Hydroida, Annals 

 arid Magazine of Natural History, March, 18IU, p. 203. 



3 British Hydroid Zoophytes, London, 1808, pp. xvii, xviii. 



J A Monograph of the Gynmoblastic or Tubiilarian Hydroids, Kay Society, London, 1870-1872, p. ll.">. 



