274 DR J. M. MACFARLANE ON THE 



spiral or spiro-reticulate thickenings on cells of Masdevallia Chelsoni, are observed 

 cases. 



For the evolutionist these have some value. Whether one adopt the view that 

 environmental surroundings are the main agents in conferring acquired characters, or 

 that these wholly arise by accidental variation, we have strong grounds for believing that 

 these acquired characters are handed down, though weakened in intensity by half. 

 Nevertheless, if these are of advantage, sexual union of the progeny, coupled with possible 

 further variation along the same line, may retain or even intensify the new character. 

 But the case of Cypripedium Leeanum is of more than ordinary interest, for not only 

 are the colour spots that are present in C. insigne and absent in C. Spicerianum inherited 

 though in less intensity of tint, by the hybrid, but we find a complete absence of hairs 

 where, under ordinary heredity transmission from C. Spicerianum, they should have been 

 formed. Now it has been repeatedly noticed that when a species varies from the normal 

 it seldom does so in one point or structural detail, but a certain variation- wave, so to 

 speak, travels through the entire organism, giving it that combined set of characters 

 which make it rank as a sub-species. The relation between colour production and hair 

 distribution already described not only shows how new characters may be imported into 

 a line of organisms, but how these may even be powerful enough to minimize the normal 

 action of the other parent. A somewhat similar case is that of Saxifraga Andrewsii, in 

 which the circumstomatic knobs inherited from the " Aizoon " parent are to all appearance 

 correlated as a morphological character, with lime secretion by the stomata as a 

 physiological one. 



(c) Bisexual Heredity. — The cases of such that have been noticed are few, and do not 

 probably possess great interest apart from hybrid study. We include under this head such 

 an example as Ribes Culverivellii, in which the simple hairs of R. Grossidaria and 

 the oil-secreting peltate hairs of R. nigrum are both separately reproduced, though about 

 half as large * as those of the parents. Saxifraga Andrewsii and Carduus Carolorum t 

 likewise have distinct types of hair inherited from both parents. No cases are known to 

 me where internal elements or tissue masses are thus separately reproduced. All the 

 hybrids in which the above has been observed are derived from parents considerably 

 removed in systematic relationship, and the incompatibility of blending the diverse types 

 of hair probably explains their appearance as separate growths. 



But the general principle here illustrated on an exaggerated scale is that the offspring 

 of two parents may inherit from each diverse peculiarities which, instead of blending 

 evenly, retain their separate individuality. Future experiment and observation alone 

 will decide for us whether these can be passed down through two, three, or more 

 generations, and till we have the evidence it would be impossible to generalize. 



* I should state here that the gland hair figured from E. nigrum (Plate V. fig. 13) is slightly larger than the average, 

 and that from the hybrid smaller, but for microphotographic work one has sometimes to choose material that shows the 

 objects, even though these are not of average size. The cell details also are lost in the figure. 



t This is a very instructive hybrid that was gathered in Inverness-shire by Messrs Jenner and Howie, and of 

 which abundant material has been secured for future description. 



