240 SECTIONAL ADDRESSES. 



the equivalent of saying that all the forms cited betray an affinity to the 

 Archegoniatse. Just as sexuality may be held to have arisen repeatedly 

 and independently in various groups of the lower organisms, so may the 

 various higher families have carried out independently the establishment 

 of two generations. Where a second generation is present we may assume 

 that it was independently interpolated, and has developed from small 

 beginnings such as we see in (Edogonium or Sphceroplea, &c.' If this be 

 admitted for various families of the Algse, it may be contemplated the 

 more readily for the Archegoniatse, which are more distinct in their 

 characters from the Algse than these are among themselves. 



No one has yet made out a closely reasoned case for the descent of the 

 Axchegoniatae from the Green, the Brown, or the Red Algas. The old- 

 view that they originated from the Green Algae has never recovered from 

 the blow delivered by Dr. Allen, when he showed that the reduction in 

 ColeochcBte takes place in the first divisions of the zygote, and that the 

 presumed primitive sporophyte is really haploid, and not cytologically a. 

 sporophyte at all. It is a perfectly tenable position to hold that the 

 Archegoniatee sprang directly from none of these groups, as we know 

 them. In the absence of definite comparative evidence the field appears 

 to be open to an origin of alternation in the Archegoniatse by interpolation 

 of a sporophyte de novo, developed not in water but in relation to a land- 

 habit. Against such an origin of a sporophyte there is in some minds a 

 strange, and to me an inexplicable, preconception. Many years ago- 

 Professor Von Goebel drew attention to a curious leaning among: 

 morphologists towards reduction-series. It appears as a prevalent 

 psychological phenomenon that men are more prone to admit down-grade 

 sequences than those that are up-grade. But it is clear that in evolution 

 at large there must have been a credit-balance of upward development 

 as a whole, otherwise no multicellular organisms could exist at all. Each 

 morphologist no doubt strikes his own financial balance at the end of the 

 year, and notes justly whether or not his credits meet his debits. * Why 

 should he not carry forward the same accurate balance of amplification 

 against reduction into his morphology ? But we find him cheerfully 

 accepting evidence of the practical elimination of the gametophyte in 

 Seed-plants, and contemplating a similar elimination in the Brown Sea- 

 weeds, thus making drafts upon his morphological account. When, how- 

 ever, an origin by interpolation of the sporophyte is suggested to him, he 

 regards this morphological asset with something more than suspicion. 

 He will overdraw his morphological balance more willingly than he will 

 pay in assets to his morphological credit. 



Here it may be well to consider what rational explanation is now possible 

 for the origin of a diploid generation. The old biological idea that the 

 alternation arose in relation to amphibious life will not suffice, since 

 alternation is seen to exist in fully aquatic Algae. Nevertheless, the 

 amphibial life may have been one of the circumstances that have modified 

 the development, and guided it into the special channel seen in Arche- 

 goniate Plants. Svedelius, however, suggests a more general reason for 

 the somatic development of a diploid sporophyte which deserves the 

 most careful attention (' Binige Bemerkungen ueber Genera tionswechsel 

 und Reduktionstheilung,' 1921). Instead of laying weight upon 



