ABSTRACTS. 6 1 



placed, and there seemed to be a slight indication of diil'ereiice of 

 sex, as the contents of one Desmid were passing to the other 

 without ii corresponding return. The wall or membrane of the 

 tube was very delicate and fragile. There are several examples 

 which have become separated from their conjugating partner and 

 show a small protuberance between the semi-cells. One specimen, 

 which can only be regarded as a monstrosity, has developed a 

 large bulging swelling, apparently well covered by a cell-v»a]l, 

 and it has continued its existence in a distorted form, deciding 

 that it would not die until it was compelled to do so. 



I think that it is quite possible that a conjugation tube may 

 be formed more frequently than it is observed ; any rough treat- 

 ment would easily destroy it. Evidence of conjugation without 

 its formation is abundant ; this is the onlv specimen which I have 

 seen with the tube really complete. 



The spores are formed in the water between the two Desmids, 

 and, at first, the protoplasm is surrounded by a gelatinous 

 coating which changes into the hardened wall and develops 

 spines. It is difficult to trace the early stages of the nucleus 

 during the process of the growth, as the oil-drops, which consti- 

 tute a prominent feature of the metabolic processes going on 

 within the zygospore, obscure the other cell-contents. When the 

 cell-contents are set free, they ultimately increase greatly in size, 

 and the oil disappears, doubtless forming food for the young 

 Desmids. If W(^ consider the nucleus of the parents to be haploid 

 and the conjugation nucleus to be diploid (of which I can offer no 

 evidence), the subsecpient division of the contents of the spore 

 into four masses is probably of the nature of a reduction division, 

 and this process may be commonly and easily seen. As previously 

 mentioned, there were great numbers of zygospores produced last 

 year, and I obtained many dozen showing this formation of four 

 " Desi.iid Mother Cells " before the contents leave the spore. The 

 oil-drops have gone, and a tetrad formation appears to have 

 taken place ; three nuclei with their surrounding protoplasm and 

 colouring matter are seen in focus at the same time, and the fourth 

 is concealed by the other three ; thev do not at first fill the spore, 

 but are widely separated from each other and arranged near the 

 spore coats; later they inci'ease in size, and the four masses of 

 protoplasm collectively fill the entire space, the division between 

 them still remaining distinct. 



The cell-contents appear to be of slightly lower specific gravity 

 than the spore-coat. The first indication of a germination is the 

 contraction of the plasma membrane, and the cell-contents, in 

 almost every instance, come to the upper surface of the sj)ore ; 

 I have seen very few dehiscing laterally — the contents escape in 

 an upward direction; possibly the empty spore-coating sinks; at 

 any rate, the contents do not remain associated w ith their former 

 abode; the empty cases do not appear in numbers proportionate 

 to those of the developing embryonic Desmids. 



Three or four nuclei may be seen in the escaping contents, and 

 four, three, two, or only one embryonic Desuiid may result ; 



