266 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the tentacles. Connexions between muscle and nerve could only be 

 established with certainty in the sub-umbrella, where the myoblasts, and 

 apparently not the muscle-fibres, are innervated. But the great 

 numbers of ganglion-cells and nerve-fibres that occur in the muscle 

 regions make it probable that the whole musculature is innervated. 

 The nerve-plexus is connected on the one hand with the musculature, 

 on the other with superficial sense-cells. Since the musculature is un- 

 doubtedly innervated and the peripheral nervous system is capable of 

 conveying stimuli to it, Kleinenberg's theory of the direct irritability of 

 the epithelial muscles (myoblasts) and their power of transmitting 

 stimuli to the muscle-fibres, appears doubtful. 



Development of Thecaphore Hydroids.*— Dr. K. Miiller Cale has 

 investigated representatives of three families, Campanulariidae, Sertu- 

 lariidae, and Plumulariidae, with a view to finding out whether the same 

 multiplicity of types of germinal layer formation obtains among them 

 as among athecate forms. In three forms, Laomedea flexuosa, Plumularia 

 echinulata, Sertularia polyzonias, the type of segmentation and germinal 

 layer formation is the same as that already known for Glava. De- 

 velopment begins with total equal segmentation, and the embryo, which 

 is solid from the first, becomes at the fifth segmentation a true multiple- 

 layered morula. From this a planula, essentially like that of Glava, 

 arises by secondary delamination. In the ova, rich in yolk, of Agla- 

 oplienia 'and Thecocarpus, there is, at the beginning of segmentation, a 

 tendency to unequal division and retardation of the division of the 

 plasma relative to the nucleus. Nevertheless, a morula like that of the 

 previously described forms results. From that stage they follow a new 

 path of development leading to a syncytial stage similar to that which, 

 in some athecate forms, follows total segmentation. In the syncytium 

 the superficial layer becomes separated by a membrane as ectoderm. 

 One peculiarity of the Aglaopheniidse lies in the fact that not nearly all 

 the segmentation-nuclei take part in the building up of the embryo-cells. 

 Many of them, both in the superficial ectodermic layer of the syncytium, 

 and "within it, become mingled with the liquefying yolk-masses, and 

 degenerate as yolk-nuclei. 



New Actinians from British Columbia. f-— J. Playfair McMurrich 

 gives an account of the structure of Peachia quinquecapiiata sp. n., and 

 Bicidium sequorese sp. n., which are of special interest because they 

 probably represent stages of a single species (of Peachia ?), and belong 

 to a group that has not yet been described as occurring on the west 

 coast of North America. The second form is not uncommon on the bell 

 of the Leptomedusoid, JEqiiorea forslcalii, which is frequent in the waters 

 of British Columbia. 



* Zool. Jahrb.. xxxvii. (1913) pp. 83-107 (2 pis. and 10 figs.). 

 + Proc. Zool. Soc, 1913, pp. 963-72 (1 pi.). 



