TKA]SISACTIO>^S OF SECTION D. 759 



In order to render this formula more determinate I consider it impossible 

 in the actual state of science, to add to it any note concei'uiuf^ either the genesis 

 or the differentiation of the spermatic cell, ui'thout restrainiiu/ its extension. More 

 specified,_it would no more apply to all the living forms, and it would cease to be 

 general, smce nothing is more diversified than the alterations of that genesis and 

 differentiation which were observed in the dilierent degrees of the organic series. 



But, such as I have expressed it, this formula, which can apply t<) every kind 

 of cells, is not the synthe.-is of the facts observed in spermatogenesis. It is not a 

 biological law, because a biological law is nothing other than the synthesis of the 

 facts. So I may say that there is no general-law existing for spermatogenesis. 

 There are no other general laws tiiau these \\hich regulate the genesis and the 

 differentiation of every kind of cells ; laws which still totally evade research, and 

 are dependent on tlie inmost constitution of organised substance. 



But no general law existing, it is evident, however, that after long comparative 

 and conscientious analytic researches, one may make the synthesis of the facts 

 and look for special laws for the ditierent groups of beings. It would be desirable' 

 that this synthetical work were made from a comparative cvtological point of view, 

 in order to avoid the false interpretations and the multiplication of useless terms! 

 Let us add that it would be also desirable that, in the synthetical summaries, as 

 well as in the statement of the researches, separate descriptions should be "■iven of 

 the facts belonging to the three periods of spermatogenesis, namely : ° 



The period of the multiplication of the mother-cells ; the period of the 

 differentiation of the spermatic cells ; and the period of the different phenomena 

 which follow the completion of the spermatozoon. The summary I have just 

 made can be considered as being the special law for the Gcmmsids and the Ixodids, 

 the only families of acarians I have studied up to this time. 



5. On the Nesllnrj Habit of Afcypus Niger, a Florida Spider. 

 By Dr. McCoOK. 



6. 0>i Gephalodiscus. Bij S. F. Harmer. 



7. On cniite 'iieiv types of ALidrrpnrarian. Sfruc/iire. 

 By G. HiiUBEiiT FuvvLEK, B.A., I'/i.D. 



The genera of Madreporaria, of whicli the anatomy has been hitherto studied, 

 appear to fall into two divisions, the one consisting of solitary forms and of colonies 

 in which the calices are free ; the other iLcluding genera in'which a eoenenchyme, 

 or common skeleton, is present ; in the former division the body-wall is supported 

 by peripheral lamellas of the mesenteries, in the latter on the spines or echinula- 

 tions of the cosnenchynue. (Fowler, 'Anatomy of the Madreporaria,' iii 

 'Q. J. Micr. Sci.,'1887.) i" . • 



Madracis aspervla, however, forms a cojnenchyinatous colony in which the 

 septa project somewhat above the general surface, and the presence of both means 

 of support for the body-wall appears to be correlated with this fact, Madracis 

 thus being morphologically intermediate between such forms as Caryophyllia and 

 Seriatopora. 



Amphihelia ramea, an imperforate coral with free calices, varies from the normal 

 types in possessing a canal-system between body-wall and corallum, these bein'j- 

 otherwise in contact ; while the peripheral lamellaj of the mesenteries are only 

 recognisable immediately round the lip. 



In Steplunmphyllia formosissiinn also the so-called costae or ridges of coral to 

 which the mesenteries are attached are in direct contact with, and form the only 

 means of support for, the bodj'-wall, this genus bearing the same relation to the 

 Eupsammidce as Amphihelia to the Ocidinidce. In the formation of strono- 

 muscle-bundles between synapticulse, as in some minor points. Stephanophyllia 



