THE PLUMULARID.E. 21 



No further investigations of importance seem to have been carried on until eleven years later. 

 In 1882 Hainauu ' brought to bear upon the sarcostyles for the first time the modern methods by 

 which the efficiency of the microscope has been so immensely increased, and succeeded in discov- 

 ering some of the most important points regarding the nature, both histological and homological, 

 of these interesting structures. This author contributed the following points: The sarcostyle is 

 composed of external ectoderm with an endodermal axis which is composed of nucleated cells, tbe 

 two being separated by the stutzlamelle. There are a few nematocysts in the end of the sarcostyle 

 in I'lumularia and many in the same place in Antennularia. The extensibility of the sarcostyle is 

 enormous, but is due to the action of muscle fibrilhw. The amu-boid movements seen in the 

 processes from the sarcostyle the author compares to the well-known "pseudopodia cells" in the 

 foot of the common Hydra, and does not believe that we have here to do with auueboid protoplasm. 

 Eegarding the morphological significance of these structures, they are degenerated polyps or 

 degraded persons of the colony, in which the mouth and stomach have been obliterated and the 

 tentacles lost. The sarcostyles originate in a proliferation of ectodermal and endodermal cells of 

 the stem, forming a process which finally breaks through the investing chitiue, which has left a 

 cup-shaped receptacle. 



In the same year (1882) C. Merejkowsky published a very important paper entitled Structure 

 et Developpement des Ni'-matophores chez les Hydroides. 2 It does not appear tbat this author was 

 aware of Hamauii's investigations, and hence the two works are the more valuable as independent 

 contributions. The figures in Merejkowsky's work add greatly to its utility and constitute by far 

 the best set of illustrations showing the morphology and development of nematopliores that have 

 yet appeared. The following is a condensed translation of the author's summary: 



First. The nematophores are composed, not of sarcode, but of an endodermal axis and an 

 ectodermal covering divided by a membrane, " stutzlamelles" (fig. 75). 



Second. Ordinarily two parts can be distinguished, the fixed and the motile, the latter being 

 composed of ectoderm alone, exhibiting anm-boid changes of form. 



Third. In the motile part the cells present a special histological type, in that the;/ are immersed 

 in a contractile, structureless protoplasm to which the movement of the organ is due, and from which 

 pseudopodia are produced (figs. 76, 77). The author suggests that this intercellular protoplasm 

 may be the aggregated ''ectoplasm'' of the individual ectoderm cells. 



Fourth. The development of the nematophores takes place in two ways. In Aglaophenia a 

 reduplication is formed in the ectoderm of the future hydranth, afterwards the endoderm enters the 

 already formed sarcostyle (figs. 78-80). In Pin malaria and probably in Anteinittlariit -the sarco- 

 style is formed by a process or swelling of the ectoderm, afterwards tilled by an invagination of the 

 endoderm. In regard to the part taken by this structure in the life of the colony, Merejkowsky 

 thinks that they are not special organs to serve a certain function, but that they are individuals or 

 degenerate polyps. Their structure is analogous to that of the hydranths, being formed of ecto- 

 derm and endoderm. The absence of a body cavity is due to degeneration. The presence of 

 nematocysts demonstrates that they serve in the defense of the colony. The best proof that they 

 are degenerate individuals lies in the fact that the hydranths, under certain conditions, are trans- 

 formed into sarcostyles. Merejkowsky has seen this take place in specimens of Plumularia 

 halecioidex (tig. 81) which were left overnight in a vessel of running water. The tentacles and 

 mouth disappeared, the whole body diminished in volume, and the entire structure presented a 

 close resemblance to a sarcostyle. The ectoderm exhibited movements characteristic of nemato- 

 pliores, sending out long threadlike processes which continually changed form and even crept up 

 the side of the hydrotheca. ' The movement was weaker than in true nematophores. The author 

 concludes by reasserting his belief in the fact that the nematophores are ^in/liiudus degeneres." 



In 1883 three important works appeared, each of which contained detailed accounts of the 

 sarcostyles. I judge from the context that no one of these authors had the opportunity to cou- 



1 Der Organismus der Hydroidpolypen. .Icnaischi- Zeitschrift fiir Naturwissi-nsehaft, XV, New Ser., VIII, 1882, 

 pp. 17, 18, 65. 



- Archives de Zoologie Experimental et Ucnrrale, X, 1882, pp. 583-610, pi. xxix A, B. 



;1 Thc writer saw a similar case in Naples, where a hyclrantli of an Aglaoplienia became disgusted with its sur- 

 roundings and began to degenerate, sending off very pronounced sarcodal processes from its ectoderm to the 

 hydrothecal walla. 



