Feb., 1904.] 



KNOWLEDGE & vSCIENTIEIC N1«:WS. 



15 



constant in the same species of animal throuf:;hout life. 

 The number may be 8, or 12, or 20, or 40, or some other 

 number, but in the human body or that of any other 

 animal the number is the same in each cell-di\ision. To 

 this statement, however, there is an exception. In the 

 divisions which lead to the formation of reproductive 

 cells, eggs or sperms, only half the usual number of 

 loops is formed, and the division of these cells is of a 

 peculiar type. The V-shaped chromosomes are replaced 

 by loops and bends and rings, and these, also, range tlicm- 

 selves in a different way. This is one of the most curious 

 facts in microscopical science. Fertilisation consists in the 

 complete union of the nuclei of two reproductive cells, 

 and if the same number of nuclear loops were always 

 formed, this number would be doubled in each genera- 

 tion, so that if we began with two we should go on to an 

 infinite number. But as each reproducti\e cell has only 

 half the proper number, the fertilised egg formed of two 

 cells again has the proper number for the species. 



Professor Farmer, of the Royal College of Science, 

 with his colleagues, Mr. J. E. S. Moore and Mr. C. E. 



Fig. I. — Diagram of a somatic 

 division showing the split 

 chromosomes, the halves of 

 which form the daughter 

 nuclei. The full number of 

 the chromosomes is not shown. 



, 2 — Diafirain of a hctcrotypc 

 divisiotl showiiif,' the character- 

 istic rings and loops which split 

 transversely to form the da^igli- 

 ter elements. As in the pre- 

 ceding figure, the full nund)erof 

 chromosomes is not shown. 



fReproduced, by permis .ion, from The Hriti^h Mcdual Jou))utI\. 



Walker, has made the remarkable discovery, which has 

 just been communicated to the Koyal and the Linnajan 

 Societies, that these peculiarities in the division of repro- 

 ductive cells occur also in cancer cells. The cancer 

 is a mass of cells in a state of furious growth, and it 

 invades and destroys the natural tissues all around it. 

 The cells of the cancer show all stages of cell-division, 

 and Professor Farmer finds in these stages the peculiari- 

 ties which properly belong to reproductive cells only. 

 In particular the number of nuclear loops is only half 

 the number present in the cell-divisions of healthy tissue. 

 Professor Farmer is a botanist, and is distinguished for 

 his researches in the microscopic structure of the cells of 

 plants. It is a remarkable fact that in the processes of 

 cell-division, reproduction, and fertilisation, the trans- 

 formations seen in plant cells are essentially the same 

 as in animal cells. The formation of the pollen of a 

 flower in the stamens affords an example of the reduction 

 of the number of the nuclear loops above mentioned to 

 half the number proper for the plant. Only after the 

 pollen nucleus has united with another in fertilisation is 

 the full number regained. Again, a fern produces not 

 seeds but spores. The nucleus of one of these spores 



contains only half the proper number of nuclt/ar loops, 

 and the divisions of the space which form the green Hat 

 growth preceding the development of the fern present 

 the peculiarities which have now been observed in cancer. 

 The theory suggested, therefore, is that cancer is llu^ 

 abnormal formation of rejiroductive tissue in parts of the 

 body where no such tissue should be, or in certain cases 

 the abnormal behaviour of reprtxluctive cells in their 

 natural position : the peculiarities of such cells being 

 associated with a tendency to rapid division. 



The theory, if true, does not completely soKe the 

 problem. The (|uestion still remains, What are the 

 causes of this outbreak of peculiar activity in the cells; 

 how can we prevent it and guard against it ? The most 

 plausible suggestion at present is that some chemical 

 compounds are protluced in the body which stimulate 

 and excite the cells to this insane and destructive fury, 

 and we still have to discover whether this is true, and 

 whether the stiniulalion can he prevented or stopped. It 

 is something, however, to ha\e more light on tlie nature 

 of the disease, to be investigating in the right direction. 

 Something is already known of the stimulation of cells to 

 division by means of reagents, and it ought to be possible 

 to discover some antidote to the tendency to division. 

 Surgery is our only remedy at present, and is sometimes 

 very successful ; but there is always the possibility that 

 the unknown causes may continue at work, and develop 

 new centres of cancerous activity. 



Zoological Notes. 



liy R. LVDEKKEK. 



Similarities of Elephants and Dugongs. 



.\t the conclusion of his memoir on the evolution of 

 the I'roboscidea, recently published in the I'kilusophual 

 Transactions, Dr. C. W . Andrews directs attention to 

 certain very remarkable resemblances existing between 

 the elephants and their extinct allies (I'roboscidea) on 

 the one hand, and the manati and dugong (Sirenia) on 

 the other. Among the features common to the two groups 

 are the non-deciduate and zonary placenta, the ab- 

 dominal testes, the pectoral position of the mamma-, the 

 bilid apex of the heart, the general absence of a foramen 

 in the lower end of the humerus, and a remarkable 

 similarity not only in the form of the molars, but likewise 

 in the mode of successitjn of these teeth, which are pushed 

 forward in the jaws with advancing age. Whereas, how- 

 ever, in the Sirenia this pushing forward is due to the 

 development of additional teeth at the back of the series, 

 in the Proboscidea it is caused by a progressive increase 

 in the size of the individual teeth from front to back. In 

 both cases the anterior molars are shed as they become 

 worn out. Other resemblances between the two groups 

 exist. .'Mtliough the evidence is far from being con- 

 clusive, yet it is strongly in favour of a relationship 

 between sirenians and proboscideans, albeit at a very re. 

 mote epoch. * :■ 



Fos.sil Reptiles. 

 In a recent issue of the Pliilusuphical 'I'l-ansailiom, Mr. 

 G. A. l^oulenger describes some interesting reptilian 

 remains from the Triassic sandstone of Lossiemouth, 

 near El^in. They include a remarkably fine skull of 

 Ilypcrudapcdou, which shows the structure of the palate 

 better than in any other known specimen. The main 

 difference from the corresponding aspect of the skull of 

 the existing tuatera {Sphcnodon) of New Zealand, apart 



