ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 47 



Structures resembling Ova.* — Prof. Mcintosh has taken near the 

 Forth certain peculiar dull yellowish structures resembling ova ; they 

 adhered to each other, and were nearly circular ; their capsule was 

 yielding, and the contents consist of a structureless gelatinous 

 substance. 



B. HistologT-t 



Morphology of the Cell-nucleus. | — Dr. W. Pfitzner comes to the 

 conclusion that the nucleus is always a completely independent 

 structure inclosed in the cell ; and that karyokinesis is the expres- 

 sion of a process going on within the cell-nucleus, in which no 

 morjihological constituents of the cell-body take any active part. 

 The first of these dicta leads to certain consequences, for it is clear 

 that a new nucleus can never arise. The extraordinary constancy 

 which is seen from the Protozoa to man leads us to believe that the 

 existence of the cell as a biological unit is connected with the 

 presence of a central body of complicated internal structure, and 

 that, therefore, the chromatin structures are not secondarily acquired, 

 but are the prime conditions of the vital existence of the cell. 

 Further, karyokinesis is not a special mode of nuclear division, but 

 is the mode Kar l^oxqv. The author recognizes that these views are 

 not those of the authorities on the subject, and he ofiers some 

 criticisms on the recent results of Flemming and Lavdowsky. 



Contraction of Striped Muscle. §— With the aid of an apparatus 

 wliich he terms the myoscope M. F. Laulanie has studied the con- 

 traction phenomena of muscles retained in their normal environment 

 and connections. He follows up his previous (1875) observations on 

 the muscles of the aquatic larva of Corefhra plumicornis, and sup- 

 plements them by a study of the phenomena exhibited by the 

 unisolated hyoid muscles of the frog. While the circulation con- 

 tinued normal in the Corefhra larva or in the frog, undoubtedly 

 simultaneous contractions were observed ; but as the circulation 

 became irregular, waves of contraction set in, progressing from either 

 extremity of the fibre, or sometimes from both ends at once, annihi- 

 lating one another as they met. While the contraction wave was 

 being observed along the fibre, simultaneous contractions also occurred 

 without apparently aifecting the former. In the frog the muscular 

 wave was but rarely observed, except in some apparently highly 

 functional fibres, and was characterized by the extreme slowness of its 

 progress, sometimes efiecting contraction only over a very limited 

 area. 



M. Laulanie distinguishes three modes of activity : (1) total and 

 simultaneous contraction (secousse) ; (2) partial contraction ; (3) mus- 

 cular wave, or partial and progressive contractions. He regards the 

 first as characteristic of normal activity in conditious where the 

 muscles retain their full excitability, and the muscular wave as 



* Tom. cit., p. 48.5. 



t This section is limited to pnpers relating to Cells and Fibres. 



X Morphol. Jahrb., xi. (1885) pp. 5i-77 (1 pi.)- 



§ Comptcs Rendus, ci. (1885) pp. G69-71. 



