mVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 483 



tomentosum, VaucJteria sessilis, and Caulerpa prolifera. In all these 

 cases a number of nuclei (often very minute) were found embedded in 

 the parietal layer of chlorophyll in the elongated tubular cell, as also 

 in the sexual reproductive cells of Vaucheria. 



In Conferva the structure in this respect was found to be various. 

 The smaller species all contained a single nucleus in each cell ; 

 while in some larger kinds there were two, multiplied by bipartition 

 before the division of the cell, so that for a short time before cell- 

 division each cell contained four nuclei. 



In Uha the presence of a single very small nucleus was deter- 

 mined in each cell ; and the same was the case in Monostroma bullosum, 

 in addition to the single large starch-grain. 



In Chlamydomonas the cell-structure is the same, whether in the 

 resting or in the gloeocystic condition. The single oviform cell 

 contains at the anterior end a funnel-shaped vacuole. At the broader 

 posterior end is a moderately large starch-grain. The rest of the 

 protoplasm is apparently of a uniform green colour, and contains a 

 smaller or larger number of protoplasmic corpuscles. Only the 

 anterior end is colourless, and contains a small spherical nucleus, 

 directly beneath the point of insertion of the cilia. A nucleus was 

 also detected in the resting cells of Euglena. 



In several species of Chroolepus and Glceocapsa the presence of a 

 nucleus was also substantiated, as also in Oscillaria princeps. 



In Saprolegnia and nearly allied genera, the following is the uni- 

 form cell-structure. The cell-wall of the tubular branched thallus is 

 completely clothed by a parietal layer of protoplasm, strings of proto- 

 plasm also passing through the cell-cavity. Embedded in the parietal 

 layer are always a number of roundish nuclei. The same structure 

 occurs in species of Peronospora, Mucor, Chytridium, &c. 



In SaccJiaromyces cercvisioi, the reagents employed discovered a 

 single spherical central nucleus in each cell, embedded in the proto- 

 plasm near the vacuole. In Oidium lactis there are several in each 

 cell. 



In the asci of the Ascosptorece, as already observed by De Bary, 

 a single original nucleus divides into two, four, and finally into eight 

 nuclei. 



In the Myxomycetes, Dr. Schmitz has at present confined his 

 attention to the plasmodia. In these were found nuclei in very largo 

 numbers. 



Tlie general conclusion arrived at from the large number of 

 observations made by Dr. Schmitz, of which only some have hero 

 been referred to, is that in all the Thallopliytcs the cells invariably 

 contain one or more nuclei, organisms destitute of a nucleus being 

 altogether unknown. It has heretofore been stated that such a condi- 

 tion may occur temporarily in the interval between the absorption of 

 a nucleus and the free-formation of fresh nuclei. This, however, has 

 never been observed by the author ; and, from analogy, ho considers it 

 pro])able it never occurs, but that, on the contrary, the presence of 

 a nucleus is absolutely essential to a living cell. 



The same he believes also to be the case in all the higlier plants, 



